A compound of the invention is a specific compound having a phosphorylcholine group, and a polymer of the invention comprises at least 1 mol % of repeating units with a phosphorylcholine group and has a number-average molecular weight of 1,000 or more, the repeating units with a phosphorylcholine group being represented by the formula (II): ##STR00001## wherein A is a bond selected from a single bond, --O--, --COO--, --OOC--, --CONH--, --NH--, --NHCO--, --NR.sup.2-- and --CH.sub.2O-- where R.sup.2 is an alkyl group having 1 to 6 carbon atoms; and m is an integer of 1 to 12.