To propose an apparatus for magnetizing a liquid, which can more efficiently induce a rotational vortex motion to the liquid to be treated by restraining an influence by a flow rate.

The apparatus 1 for magnetizing the liquid is provided with; a housing pipe 21 through which a coolant liquid is circulated; a magnetic vibration element 31 arranged inside the housing pipe 21; and a magnetism generating means 41 which is arranged outside the housing pipe 21 and can magnetize the magnetic vibration element 31. In particular, a spiral member 51 for generating the rotational vortex motion in the coolant liquid flowing in an arranged place of the magnetic vibration element 31 and the magnetism generating means 41 is arranged on the upstream side of the arranged place thereof. As a result, the rotational vortex motion is generated in the coolant liquid flowing in a treatment area 25 by the spiral member 51 and the coolant liquid is made to flow in the treatment area 25 as a spiral flow.