Oil supply device

An oil supply device that supplies oil, comprising:

• a pump configured to pump oil;
• and
• a spool switch valve that has a spool in which a first land and a second land are coupled in an axial direction at a predetermined interval therebetween, and a housing accommodating the spool so that the spool can move in the axial direction, having an input port configured to receive the oil pumped from the pump, an output port configured to output the received oil, and a drain port configured to discharge the received oil, and having a first oil chamber defined therein by opposing surfaces of the first land and the second land, wherein
• the spool has the plurality of lands so that when located at a first position, the spool seals between the input port and the output port by the second land and allows the input port to communicate with the drain port, and when located at a second position, the spool allows the input port to communicate with the output port via the first oil chamber and seals between the input port and the drain port by the second land,
• the housing has a first seal surface on which the drain port is formed, and
• when located at the second position, the second land seals the first seal surface and the second land is placed on the first seal surface at an area that axially overlaps the drain port in order to completely cover the drain port and at an area between the drain port and the input port.