To provide a pump, reduced in size and having simple structure.

A piston 2 formed by a permanent magnet slidably inserted in a hollow case 1 to partition a space A in the case 1 is moved by coils L1, L3 to expand and contract the space A alternately, thereby changing the capacity of the space A. Thus, a fluid introduced into the space A is discharged. Accordingly, a motion converting mechanism for converting the rotary motion of a motor to the linear motion is not required unlike the conventional pump, so that the pump can be reduced in size. Further, the structure can be simplified by dispensing with the above motion converting mechanism.