To provide a small-size and highly efficient seal-less pump by dispensing with a filter of fine texture.

This seal-less pump is so constituted that a pump 1 is constituted of a casing 10, an impeller 20, a motor 30, and a magnetic bearing 40, rotary members and bearing members of the motor 30 including the impeller 20 and the rotary shaft 35 are arranged in a liquid contact part of the casing 10, and other constitution members including a stator 33 are arranged in an atmosphere side across a diaphragm of the casing. The impeller 20 having a field magnet 32 in the back face is levitated and supported in non-contact with a liquid chamber by magnetic bearing 41, 42, and 45 attached to the rotary shaft 35, and a rotation field is generated by energizing to a coil 34 of the stator arranged opposite to the field magnet 32 so that the impeller 20 is rotated and cooling water sucked from a suction port 15 is discharged from a discharge port 17 via the impeller 20 and a spiral chamber 16.