A popular myth amongst men is that married women become upset if they discover that their husband is masturbating. While it can be said that who/what he is masturbating to may indeed upset her (LOL @ the poor woman who walks in on her spouse masturbating to Warren Beatty!), few women will prefer the man who demands she have sex with him whenever he wants to the man who respects her bounds as an autonomous human being and who recognizes that her desire to have sex (or to not have sex) matters just as much as his own does.
Yes, married men masturbate. Not all, but I daresay the vast, vast majority.
It may surprise you to know (lol) that married women masturbate, too. Many men will say that only women who are sexually unfulfilled masturbate (b/c women notoriously seek sex much less often than guys do), but this isn't true on a case-by-case basis nor does it still rule out the fact that women may be in the mood at times that are inopportune for their men. For example, she may really want to have sex but you may be out camping in Minnesota with the boys. Which would you prefer she do: masturbate with her fingers, a dildo, and a vibrator? or call over a gigolo to fuck her vagina until it's as red as a tomato?