PURPOSE: To form a supporting system of moving part having the height within the sum of the diameter of rotary member and that of guide shaft, and to make a linear actuator thin by dispersedly arranging rotary members to two pairs of guide shafts.

CONSTITUTION: When a current is made to flow in a driving coil 7 by a driving circuit, a magnetic flux perpendicular to the direction of current flowing in the coil 7 is generated by a magnetic circuit 8, and an electromagnetic force in the moving direction 4 is generated in the coil 7. So, the electromagnetic force exerted to the coil 7 is transmitted to the moving part 3, and the moving part 3 supported through the rotary members 6 against the guide shafts 5 is moved to the direction 4. Thus, by providing two pairs of guide shafts 5 in the downward space of a cartridge 1, the rotary members 6 are dispersedly arranged in a plain-like form, and the supporting part can be formed smaller in height than the sum of the diameter of member 6 and diameter of shaft 5, then the linear actuator can be made thin.