A fuel reforming device comprising: a combustion part (110, 11); a burner installed in the combustion part (110, 11); an exhaust part through which an exhaust gas generated from the combustion part (110, 11) is discharged; and a reactor (131, 132, 133) provided near the combustion part (110, 11) or the exhaust part, generating hydrogen from a raw material by absorbing heat from the exhaust gas passing through the combustion part (110, 11) or the exhaust part, wherein the reactor (131, 132, 133) is a steam-reformer, wherein the reactor (131, 132, 133) is provided with a heat storage member that absorbs heat during operation of the combustion part (110, 11) and stores the absorbed heat therein to provide heat required by the reactor to the reactor (131, 132, 133), wherein the heat storage member is formed in a shape of a plurality of balls filled in the reactor (131, 132, 133); wherein the heat storage member is provided with a phase change portion constituting a phase change material inside a surface portion, the phase change portion being made of a material having a melting temperature lower than that of the surface portion and/or latent heat higher than that of the surface portion, wherein the reactor is provided with at least one splitter for splitting the reactor into two or more spaces, and the heat storage member is arranged at the two or more spaces of the reactor, and wherein the splitter is made of a material of which melting temperature is higher than that of the heat storage member, characterized in that the fuel reforming device further comprises a temperature controller for maintaining a temperature of the heat storage member, wherein the temperature controller includes: a plurality of temperature sensors (171a, 171b, 171c) installed along a moving direction of the exhaust gas, detecting a temperature of the reactor (131, 132, 133) and a controller controlling an operation of the burner by comparing temperatures detected by the temperature sensors (171a, 171b, 171c) with the melting temperature of the heat storage member, wherein the controller is adapted to control the burner to allow the lowest one of the temperatures detected by the temperature sensors (171a, 171b, 171c) to be maintained or to be higher than the melting temperature of the heat storage member. a combustion part (110, 11); a burner installed in the combustion part (110, 11); an exhaust part through which an exhaust gas generated from the combustion part (110, 11) is discharged; and a reactor (131, 132, 133) provided near the combustion part (110, 11) or the exhaust part, generating hydrogen from a raw material by absorbing heat from the exhaust gas passing through the combustion part (110, 11) or the exhaust part, wherein the reactor (131, 132, 133) is a steam-reformer, wherein the reactor (131, 132, 133) is provided with a heat storage member that absorbs heat during operation of the combustion part (110, 11) and stores the absorbed heat therein to provide heat required by the reactor to the reactor (131, 132, 133), wherein the heat storage member is formed in a shape of a plurality of balls filled in the reactor (131, 132, 133); wherein the heat storage member is provided with a phase change portion constituting a phase change material inside a surface portion, the phase change portion being made of a material having a melting temperature lower than that of the surface portion and/or latent heat higher than that of the surface portion, wherein the reactor is provided with at least one splitter for splitting the reactor into two or more spaces, and the heat storage member is arranged at the two or more spaces of the reactor, and wherein the splitter is made of a material of which melting temperature is higher than that of the heat storage member, characterized in that the fuel reforming device further comprises a temperature controller for maintaining a temperature of the heat storage member, wherein the temperature controller includes: a plurality of temperature sensors (171a, 171b, 171c) installed along a moving direction of the exhaust gas, detecting a temperature of the reactor (131, 132, 133) and a controller controlling an operation of the burner by comparing temperatures detected by the temperature sensors (171a, 171b, 171c) with the melting temperature of the heat storage member, a plurality of temperature sensors (171a, 171b, 171c) installed along a moving direction of the exhaust gas, detecting a temperature of the reactor (131, 132, 133) and a controller controlling an operation of the burner by comparing temperatures detected by the temperature sensors (171a, 171b, 171c) with the melting temperature of the heat storage member, wherein the controller is adapted to control the burner to allow the lowest one of the temperatures detected by the temperature sensors (171a, 171b, 171c) to be maintained or to be higher than the melting temperature of the heat storage member.