Provided is a linear actuator which is simple in structure, inexpensive to manufacture, in addition, has small magnetic leakage, and can provide a large inertial force without increasing the number of parts and weight.The linear actuator is provided with an output shaft 12 which is supported on a supporting case 11 so as to linearly reciprocate freely, an elastic member 13 which biases the output shaft 12 toward a middle position of the linear reciprocation thereof, a permanent magnet 14 which is fixed to the output shaft 12, a coil 15 which linearly reciprocates the output shaft 12 by having a variable magnetic field act on the permanent magnet 14 and is fixed to the supporting case 11 such that the coil 15 faces one of magnetic poles of the permanent magnet 14, a yoke 16, which is composed of a magnetic material, has a midway portion tightly secured to the other magnetic pole of the permanent magnet 14, extends to the exterior of the coil 15 along the exterior of the permanent magnet 14 with a space from the permanent magnet 14, and has an end portion disposed close to the exterior of the coil 15, and power supply means for forming a variable magnetic field on the coil 15.