In an expandable part positioned on the tip end side of the catheter, protruding parts are produced in specific regions when the expandable part is expanded through the difference in elasticity between two materials having a different elasticity to one another. The structure is made to be such that low-elasticity regions and high-elasticity regions are disposed in the expandable part, and when pressure is applied the high-elasticity regions expand more than the low-elasticity regions, thus becoming the protruding parts. Alternatively, the structure is made to be such that two materials having a different elasticity to one another are made into a two-layer structure of an inner layer and an outer layer, and voids are provided in the layer formed from the low-elasticity material, so that when pressure is applied, parts of the layer formed from the high-elasticity material corresponding to the void parts become the protruding parts.