Recently, thin-type permanent magnet have been increasingly used to reduce the size of motors and actuators. However, the characteristics of a permanent magnet defetiorate when it is thinned. The demagnetization of a magnet leads to a design that miniaturized the motor and actuator. We developed a low power, thin linear oscillatory actuator (LOA) for cellular phones. A thin-type permanent magnet is used for the LOA. The characteristics of the LOA might be adversely affected by demagnetization of a thin-type permanent magnet. This paper describes (1) the structure and operating principle of the LOA for cellular phones, (2) considerations on the coercive force based on the thrust characteristics of the LOA, and (3) considerations of coercive force based on measurement of the magnetic flux density.