A bone resection jig that can make ligament tension equal at extension and flexion positions without any actual measurements when resecting femur and tibia during artificial knee joint replacement surgery. The bone resection jig used in artificial knee joint replacement surgery includes a spacer block (1) comprised of a grip (6), a hollow box (7) that is provided on an other end side of the grip and has a vertical hole (7a) therein, and a reference spacer part (8) that extends out from the hollow box (7) and is adapted be inserted into the resection region between femur and tibia； a reference pin guide (2) which, when the femur and tibia are in the flexion position, is inserted into the vertical hole (7a) of the hollow box, extends on the reference spacer part (8) to the other end side of the grip so as to come into contact with a resection plane (FH) of the tip of the distal end of the femur, and is formed with guide holes (9) for guiding reference pins (3) to be installed from a front side into the resection plane (FH) of the tip of the distal end of the femur； and an aiming member (12) which is, after the spacer block (1) has been removed from a space between the femur and tibia leaving the reference pins (3), brought onto the reference pins (3) by being guided thereby, the aiming member being provided with an indicator (14) that indicates a resection plane (FR) at a back of the distal end of the femur when the aiming member (12) comes into contact with the resection plane (FH) of the tip of the distal end of the femur.
