An oil storage tank includes a step member, a first tank part and a second tank part. The step member has a placement face. The first tank part is disposed below the step member to support the step member. The second tank part is coupled to the first tank part and has an upper face a lower face, a first side face, a second side face and a recessed section. The upper face is provided above the placement face. The first side face faces the first tank part and is connected to the upper face and the lower face. The second side face is connected to the upper face, the lower face and the first side face. The recessed section is formed by a sloped face provided to a corner portion at which the upper face, the first side face and the second side face intersect.