This invention provides an emergency stop apparatus for an elevator and an elevator system, with which it is possible to keep the size of the braking elements small, minimize fluctuations in the braking force, increase the efficiency of power utilization, and minimize fluctuations in the deceleration rate. This emergency stop apparatus for an elevator is provided with: a braking element (23) that has a first sliding surface (23a), for pushing against a guide rail (8) and generating braking force; a movable member (22) having a second sliding surface (22a) contacting the first sliding surface (23a); and an elastic body (24) for applying to the first sliding surface (23a) pushing force to push the braking element (23) against the guide rail (8). The braking element (23) is configured to be movable in the vertical direction relative to the moveable member (22) by sliding of the first and second sliding surfaces (22a, 23a), and the elastic body (24) is configured such that as the locations of contact the contact part (25) of the first and second sliding surfaces (22a, 23a) move upward, the pushing force (F1) increases, and falls after reaching the maximum value.