An engine includes a reformer, a reforming-air adjuster, a reforming-fuel supply unit, a reformed-gas adjuster, and a control unit. The reformer is configured to reform fuel into a reformed gas. When a start signal is input, the control unit controls the reforming-air adjuster and the reforming-fuel supply unit to a reformable state in which the fuel is reformable in the reformer, and the control unit controls the reformed-gas adjuster so that the reformed gas flows through the reformed-gas adjuster with a degree of opening smaller than a normal degree of opening that is a degree of opening of the reformed-gas adjuster when composition of the reformed gas is in a stable state before the composition of the reformed gas becomes in the stable state, for a given period of time including at least a period immediately after the engine starts.