A bone resection jig for an artificial knee joint replacement surgery, in which a back of a distal end of a femur in a flexion position is resected after a tip of the distal end of the femur and a tip of a proximal end of a tibia in an extension position are resected horizontally, the bone resection jig comprising: a spacer block comprised of a grip, a hollow box that is provided on another end side of the grip and has a vertical hole therein, and a reference spacer part that extends out from the hollow box and is adapted to be inserted into a resection region between femur and tibia; characterized by further comprising: a reference pin guide extending on the reference spacer part to the other end side of the grip so as to come into contact with a resection plane of the tip of the distal end of the femur, and being formed with guide holes for guiding reference pins to be installed from a front side into the resection plane of the tip of the distal end of the femur, wherein a base of the reference pin guide is insertable into the vertical hole of the hollow box and an aiming member being provided with guide holes into which the reference pins are insertable such that the guide holes and the reference pins are so configured to guide the aiming member thereinto after the spacer block is removed from the resection region between femur and tibia and with an indicator that indicates a resection plane at a back of the distal end of the femur when the aiming member comes into contact with the resection plane of the tip of the distal end of the femur a spacer block comprised of a grip, a hollow box that is provided on another end side of the grip and has a vertical hole therein, and a reference spacer part that extends out from the hollow box and is adapted to be inserted into a resection region between femur and tibia; characterized by further comprising: a reference pin guide extending on the reference spacer part to the other end side of the grip so as to come into contact with a resection plane of the tip of the distal end of the femur, and being formed with guide holes for guiding reference pins to be installed from a front side into the resection plane of the tip of the distal end of the femur, wherein a base of the reference pin guide is insertable into the vertical hole of the hollow box and an aiming member being provided with guide holes into which the reference pins are insertable such that the guide holes and the reference pins are so configured to guide the aiming member thereinto after the spacer block is removed from the resection region between femur and tibia and with an indicator that indicates a resection plane at a back of the distal end of the femur when the aiming member comes into contact with the resection plane of the tip of the distal end of the femur a reference pin guide extending on the reference spacer part to the other end side of the grip so as to come into contact with a resection plane of the tip of the distal end of the femur, and being formed with guide holes for guiding reference pins to be installed from a front side into the resection plane of the tip of the distal end of the femur, wherein a base of the reference pin guide is insertable into the vertical hole of the hollow box and an aiming member being provided with guide holes into which the reference pins are insertable such that the guide holes and the reference pins are so configured to guide the aiming member thereinto after the spacer block is removed from the resection region between femur and tibia and with an indicator that indicates a resection plane at a back of the distal end of the femur when the aiming member comes into contact with the resection plane of the tip of the distal end of the femur