An oil storage tank includes a hydraulic oil tank configured to store hydraulic oil, a fuel oil tank configured to store fuel oil, a breather valve disposed on the hydraulic oil tank, and a breather hose connected to the breather valve. The hydraulic oil tank includes a first facing face facing the fuel oil tank. The fuel oil tank includes a second facing face facing the hydraulic oil tank. The second facing face has a fuel-oil-tank adjacent face and a fuel-oil-tank sloped face. The fuel-oil-tank adjacent face extends along the hydraulic oil tank. The fuel-oil-tank sloped face is connected to the fuel-oil-tank adjacent face and slopes relative to the fuel-oil-tank adjacent face so as to be away from the hydraulic oil tank. The breather hose is disposed along the fuel-oil-tank sloped face.