A stroke simulator in a brake system includes a cylinder body, a piston movably inserted in the cylinder body, and a second elastic member adapted to be pressed by the piston. It functions to give a simulative operational feel to a brake lever by operating the brake lever to generate a fluid pressure in a front wheel master cylinder and transmit this fluid pressure to the cylinder body, thereby deforming the second elastic member through the piston, and wherein annular recesses are formed on the outer circumferential surface of the second elastic member.