PURPOSE: To enable a permanent magnet to be easily separated with a slight force, from a magnet type retaining device (a magnet holder) with the permanent magnet to be used for.

CONSTITUTION: On a door side base body 7, a permanent magnet 1 is fixed, and a main body side base body 8 is provided with an electromagnet 4 consisting of a core 2 and a coil 3, and a door is kept in a closed state by an attraction to the core of the permanent magnet. When the door is opened, then direct current is permitted to flow to terminals 5, 6, and on the core, a magnetic pole to be repulsed to the permanent magnet is generated, and they are easily released.