An object of the present invention is to provide a brake apparatus capable of highly accurately detecting a stroke amount of a brake pedal. According to an aspect of the present invention, a brake apparatus includes a master cylinder unit and a stroke sensor. The master cylinder unit includes therein a piston configured to carry out a stroke via a rod axially actuated according to an operation performed by a driver on a brake pedal, and an oil passage through which brake fluid flows after flowing out according to the stroke of the piston. The stroke sensor is attached to an outer wall of the master cylinder unit and configured to detect an axial stroke amount of the piston.