A polymer comprising at least 1% by mole of a structural unit represented by Formula (2); in Formula (2), two R1s are the same or different from each other and are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; X is a single bond, an oxygen atom, or a group represented by —COO—, —OOC—, —CONH—, —NH—, —NHCO—, —NR3—, or —CH2O—; Y is a single bond or an oligooxyalkylene group; two R2s are the same or different from each other and are each an alkyl group having 1 to 6 carbon atoms; R3 is an alkyl group having 1 to 6 carbon atoms; m is an integer of 1 to 10; and n is an integer of 2 to 10; and having a number average molecular weight of 5,000 or more has various characteristics suitable for use in contact with a living organism and can be easily produced.