You can (though nowadays using "he" there is perceived as rather formal, so perhaps you should say "it is he" instead of using the contraction). https://www.quickanddirtytips.com/education/grammar/it-is-i-versus-it-is-me https://www.dictionary.com/e/it-is-i-vs-its-me/ https://english.stackexchange.com/questions/4032/which-is-correct-this-is-her-or-this-is-she https://english.stackexchange.com/questions/121198/i-didnt-realize-it-was-him https://english.stackexchange.com/questions/298253/it-was-he-it-was-him/298259

Hello Olena, You need an object pronoun {me, you, him, her, it, us, you, them} For example, you wouldn't say "it's I" you would say "it's me." In other words, you cannot say "it's he" because "he" is a subject pronoun. Hope that helps, Chase

Это как падежи в русском языке, надо просто тупо запоминать. it's him - правильный вариант.