The purpose of the present invention is to provide: a balloon for a catheter, the entire membrane of which having improved compliance characteristics； and a balloon catheter.This balloon for a catheter has a membrane-like body which can be expanded and contracted by fluid supplied from a catheter. The membrane-like body is provided with an intermediate layer which consists of a non-elastomer material, an outer layer which is disposed on the outer peripheral surface of the intermediate layer and which contains elastomer, and an inner layer which is disposed on the inner surface of the intermediate layer and which contains elastomer. The balloon is characterized in that the average membrane thickness of the intermediate layer is in the range of 30% to 70% of the membrane thickness of the entire balloon.
