A catheter balloon exhibiting improved pressure resistance of the entire membrane is formed of a membrane as a laminate of at least two layers including a polyamide elastomer layer and a polyamide layer, in which the polyamide elastomer layer is disposed at the inner side of the polyamide layer, a refractive index nr1 in the circumferential direction of a cross-section perpendicular to the axis in the inner side surface of the polyamide layer is greater than a refractive index nr2 in the circumferential direction of a cross-section perpendicular to the axis in the inner side surface of the polyamide elastomer layer, and the difference between the refractive index nr1 and the refractive index nr2 is 0.01 or greater.
