What can i do now for my brother?

My brother got a chance in a university in Japan and applied for CEO but the CEO was rejected because the guarantor's income statement was given for one year. After few sessions for covid, he could not reapply. After that he applied again for job visa CEO but it was also rejected.they inform us that the immigration is not satisfied with his experience certificate.Now What should my brother do? Now should I try again for student visa. He is suffering from depression now. Please give me some suggestion.

You should let you brother handle it. He is an adult.

Good on you for supporting your brother.
I don't have any practical info, sorry but ignore H's reply, that's shitty.

He is suffering from depression now
And you think that by 'trying' to apply for visa will help? the stress of waiting or getting another rejection will just add more frustration. Or does it even really related?
And also if "your brother" get into Japan, do you think that will help "his" depression. FYI, being away in foreign country alone, with no one to hold his hand, and also Japan is the worst place for depression support, some more if you don't speak the language.

You could try applying for visa again BUT have you/"your brother" rectify or overcome the rejection requirement? It is just pointless, waste of time/money to keep repeating the same thing.

they inform us that the immigration is not satisfied with his experience certificate.Now What should my brother do
Duh..get more work experience?!
What COE visa did "he"/company applied for ? What is "his" qualification/work experience?
Don't waste time/money for Student visa (for language school).

「He is suffering from depression now.」

At the risk of sounding unkind, if your brother is suffering from depression, I would strongly advise against moving to Japan. Moving overseas involves many mental/emotional challenges, even if you're moving to a country you feel a very strong attraction to.

It's kind of you to support your brother, but the fact that he's having his sibling ask for help with the technical aspects of such an important life decision on an open English forum makes me think that he doesn't speak much Japanese/have much knowledge of Japanese society (such as which governmental departments are in charge of such immigration questions), so I think he will have an especially stressful transition to life in Japan, especially since Japan is much less active in mental health care than many other countries are these days. It would be best for him to settle his mental health issues before trying to move overseas.

So, you applied for a CoE and were rejected on two different grounds. One, the guarantor was bad, and second your brother does not have the experience/qualifications required. Welcome to the real world - you don't simply get a CoE and right to live in Japan because you apply. You actually need to satisfy requirements.
Fix the income of the guarantor (get a better one), and get the required qualifications and experience. Without quals and exp, why would someone employ your brother? Why are they wanting to come to Japan?? You can't fix your brother's problems, those are his to sort out.