This paper proposes a new friction force estimator advantageous in an admittance controller. The input force to the admittance controller is obtained from an external force estimator using the friction force estimator. The friction force estimator attenuates the output force in the static friction state. The rate of the attenuation is dominated by a parameter, and strongly affects the tendency to move or stop of robots, to which the admittance controller is applied. This paper achieves the both of the sensitivity of the robots to the external force and the easiness to stop the robots by employing variable attenuation rate. The proposed method was validated using an industrial manipulator Yaskawa MOTOMAN-HP3J.