An object of the present invention is to provide a stroke simulator capable of suppressing occurrence of inclination of a piston with respect to a sliding surface formed in a cylinder. The stroke simulator includes a simulator piston (2a) which is displaced by sliding on a sliding surface (205) formed in a first cylinder (201), in response to a hydraulic pressure which is generated in a master cylinder due to an operation of a brake pedal by a driver, and a first return spring which is housed in the first cylinder (201) and applies, to the simulator piston (2a), a reaction force which is generated by an elastic deformation of the spring under a pressing force due to a displacement of the simulator piston (2a), and generates the reaction force which is applied to the simulator piston (2a) as a brake reaction force for a brake operating element. The stroke simulator is characterized in that a cup seal (201b) for sealing a gap formed between the sliding surface (205) and the simulator piston (2a) is mounted in the center (CL) in the axial direction of the sliding surface (205).