FUEL TANK OF WORKING VEHICLE

A fuel tank includes an upper surface portion, a bottom surface portion, and a peripheral wall portion, and a weir portion vertically arranged at the bottom surface portion and causing a fuel in a predetermined amount to stay in a predetermined position of an inner portion when a vehicle body is inclined. The peripheral wall portion includes a first wall and a second wall which is perpendicular to and continuous with one end side of the first wall. The weir portion includes a first weir, a second weir, a third weir parallel to the first weir, a fourth weir parallel to the first weir and arranged between the first weir and the third weir, and a fifth weir interconnecting the third weir and the fourth weir.