<p>A fuel tank (12) is constructed such that a front flange portion (14A1) of a top surface plate (14A) of a second plate (14) extends furthermore to an outside in relation to a front surface plate (13B) of a first plate (13). As a result, a front surplus space portion (15A) projected in the upper and lower directions in a range of the front flange portion (14A1) of the top surface plate (14A) is formed in the front surface side of the front surface plate (13B). A urea water tank (24) is arranged along the fuel tank (12) in such a manner that a rear side portion thereof enters into the front surplus space portion (15A). Therefore, the rear side portion of the urea water tank (24) can enter into the front surplus space portion (15A) using the front surplus space portion (15A) formed in the fuel tank (12), thereby increasing the tank capacity without downsizing the article accommodating box (16).</p>
