An axial force testing device includes a spindle and a frame. Multiple mediate members are mounted to the spindle which is rotatable relative to the frame by the mediate members. A first fixing member is connected to a first end of a scale which shows the axial force. A first contact member contacts the first fixing member and is mounted to the spindle. A second fixing member is connected to a second end of the scale. A second contact member contacts the second fixing member and is mounted to the spindle. The second contact member has a first contact portion which contacts the mediate members. A locking member is locked to the spindle and presses the first contact member, the first fixing member, the scale, the second fixing member, the second contact member and the mediate members. The axial force applied to the mediate members is displayed on the scale.