A suction strainer provided in a tank in which oil is stored includes a filtration section having a tubular shape formed by bending a thin plate into a pleated shape, a first end member and a second end member covering respective both ends of the filtration section, and a float provided on the first end member. The filtration section is provided along a horizontal direction. A tubular portion has an air vent hole having one end opening to a first hole and the other end opening to the inside of the tank. The float is provided to be movable between a position where the air vent hole is closed and a position where the air vent hole is opened.