There are provided a polyalkenyl ether type polyurethane, which is excellent in flexibility, aor the like, and which has in the molecule, a structural unit represented by formula (XXX): ##STR00001## (wherein n represents an integer of 2 to 1000, R.sup.1 represents substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted aralkyl, and R.sup.2, R.sup.3 and R.sup.4, which are the same or different, each represent a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl or substituted or unsubstituted aralkyl, and R.sup.1s, R.sup.2s, R.sup.3s, and R.sup.4s, when they are each present two or more in number, may be respectively the same or different), and the like.