Mesh force of gears due to transmission errors causes the housing vibration through shaft and bearings. In this force transmission, gear and bearing stiffness have the important role. Gears and rolling bearings have the time-varying stiffness. This work analyzes the time-varying stiffness of spur gears and the roller bearing. The sinusoidal time-varying stiffness of the roller bearing was obtained. The stiffness of spur gears and the rolling bearing were applied to 3 DOF equations of motion. As the results, bearing stiffness caused to change the first and second natural frequency and did not change the third natural frequency.