PURPOSE: To enhance the purifying effect of an oil tank type air cleaner so as to miniaturize the same, and to restrain oil from being carried away from an purifying air outlet chamber due to a capillary phenomenon.

CONSTITUTION: An oil tank 3 is removably attached to the lower part of a case body 2 of an aircleaner 1. In the case body 2, an ambient air inverting chamber 4, a filter chamber 5 and a purified air outlet chamber 6 are arranged upward in that order, and are communicated with one another, and further, an ambient air suction port 7 in the upper part of the case body 2 is communicated with the ambient air inverting chamber 4 through the intermediary of an ambient air suction passage 8 which longitudinally pierces the center part of the case body 2. A filter element 9 located in the filter chamber 5 is split into elements 9a, 9b between which a filter space 10 is defined.