A reducing agent tank includes a tank body storing reducing agent and a cylindrical gauge member visually indicating a storage amount of the reducing agent inside the tank body. The gauge member is in communication with an inside of the tank body. The tank body has a replenishment port to replenish the reducing agent. The gauge member is provided on a first wall surface of a plurality of wall surfaces defining the tank body. The gauge member is provided in a slanted manner relative to a bottom plate of the tank body. The replenishing port and the gauge member are disposed in a row along a direction that extends along the first wall surface as seen in a plan view.