An oil suction device including a primary suction port installed at an inflow end of a thin pipe for sucking oil in an oil storing section, and a third suction port formed in a gap between a first tapered surface and a second papered surface due to a relative movement of the thin pipe to the thick pipe. At a suction pressure of the oil pump less than a predetermined pressure, the oil suction device sucks only oil from the primary suction port, and at a suction pressure of the oil pump equal to or more than the predetermined pressure, air is sucked from the third suction port formed in a gap between the first tapered surface and a second tapered surface due to the relative movement of the thin pipe to the thick pipe.