Disclosed is an installation structure of a pedal stroke sensor configured to measure a displacement of a moving member interworking according to a stepping force of a brake pedal. The pedal stroke sensor provided with a sensing member to sense a change in displacement according to movement of the moving member in a non-contact manner is installed at an outside of a housing that allows the moving member to be slid thereinto, the sensing member is provided with a sensor housing that is detachably installed at the outside of the housing, a hall IC (integrated circuit) provided in the sensor housing to sense change in magnetic force, and a magnet housing provided in the sensor housing so as to move while facing the hall IC and on which a magnet is installed, and an elongated hole is formed through an outer surface of the housing in a direction in which the moving member moves, and the moving member is connected to the magnet housing by using a connecting member such that the moving member moves together with the magnet housing through the elongated hole.