To provide a fuel supply determination device improving the accuracy of determining that fuel has been supplied to the fuel tank of a vehicle.

When the variation quantity L of a residual fuel quantity L exceeds a regulation value Fb and an ignition switch has been switched from on to off, a residual fuel Lc calculated pursuant to the hysteresis of stored residual fuel quantity L is then stored as an off-time residual fuel quantity FLOFF (S430). Then, it is determined that fuel has been supplied to the fuel tank on condition that the difference in the residual fuel quantity between the off-time residual fuel quantity FLOFF and the residual fuel quantity when the ignition switch is turned from an OFF state to an ON state next time is found to be equal to or more than a determined value.