An electric brake system includes a linear motion mechanism for converting the rotation of a rotary shaft to a linear motion of an outer ring member, and configured such that the friction pad is pressed against the brake disk by the outer ring member. The brake system further includes a reaction force receiving member adapted to receive an axially rearward reaction force generated when the friction pad is moved axially forwardly and pressed against the brake disk, and a stationary member provided axially rearward of the reaction force receiving member. A magnetic pole row is mounted to the reaction force receiving member, while the magnetic sensor is mounted to the stationary member.