A reforming system may include an engine; an intake line connected to the engine; an exhaust line connected to the engine; a reformer provided at an exhaust gas recirculation (EGR) line diverging from the exhaust line and mixing the exhaust gas with fuel; a front end pressure sensor provided at the EGR line of the front end portion of the reformer and measuring pressure of the exhaust gas of the front end portion of the reformer; a rear end pressure sensor provided at the EGR line of the rear end portion of the reformer and measuring pressure of the exhaust gas of the rear end portion of the reformer; and a reforming controller configured for determining whether reforming continues on the basis of a pressure difference between the front end portion and the rear end portion of the reformer measured by the front end and the rear end sensors.