A solid oxide fuel cell device for generating electricity by causing an electro-chemical reaction of fuel gas and oxidant gas, comprising: solid oxide fuel cells disposed within a solid oxide fuel cell module; a reformer for reforming fuel gas and supplying the fuel gas to the fuel cells; by executing any one of the reforming reaction POX, wherein fuel gas is partial oxidation-reformed by causing a chemical reaction between a fuel gas and an oxidizing gas in a predetermined temperature band, the reforming reaction SR, wherein fuel gas is steam reformed by chemically reacting a fuel gas and steam, and the reforming reaction ATR, wherein fuel gas is auto-thermally reformed by the combined use of POX and SR; a reforming state temperature detector for detecting the reforming state temperature in order to change the reforming state induced by the reformer; and a controller for controlling the operation of the fuel cell module; wherein the controller has a startup control device for controlling the startup of the operation fuel cell module, and a stop control device for controlling the stopping of the fuel cell module; wherein the startup control device executes a combustion operation to rise the temperature of the reformer by the combustion heat of the fuel gas when after the fuel gas is ignited and caused to combust, the reforming state temperature detected by the reforming state temperature detector is lower than the POX starting temperature at which POX starts; the startup control device executes a normal startup POX to raise the temperature of the reformer when the reforming state temperature is equal to or greater than the POX starting temperature and within a POX temperature band below the temperature at which steam reforming is possible; the startup control device executes a normal startup ATR to raise the temperature of the reformer when the reforming state temperature is equal to or greater than the temperature at which steam reforming is possible, and is within the ATR temperature band below a predetermined steady state temperature; and the startup control device executes a normal startup SR when the reforming state temperature is equal to or greater than the predetermined steady-state temperature; characterized in that the startup control device further executes a restart control by the ATR, skipping the normal startup POX, if stop processing by the stop control device is executed in association with stopping of the fuel cell module from a high temperature state, and a restart of operation is executed when the reforming state temperature is within the POX temperature band. solid oxide fuel cells disposed within a solid oxide fuel cell module; a reformer for reforming fuel gas and supplying the fuel gas to the fuel cells; by executing any one of the reforming reaction POX, wherein fuel gas is partial oxidation-reformed by causing a chemical reaction between a fuel gas and an oxidizing gas in a predetermined temperature band, the reforming reaction SR, wherein fuel gas is steam reformed by chemically reacting a fuel gas and steam, and the reforming reaction ATR, wherein fuel gas is auto-thermally reformed by the combined use of POX and SR; a reforming state temperature detector for detecting the reforming state temperature in order to change the reforming state induced by the reformer; and a controller for controlling the operation of the fuel cell module; wherein the controller has a startup control device for controlling the startup of the operation fuel cell module, and a stop control device for controlling the stopping of the fuel cell module; wherein the startup control device executes a combustion operation to rise the temperature of the reformer by the combustion heat of the fuel gas when after the fuel gas is ignited and caused to combust, the reforming state temperature detected by the reforming state temperature detector is lower than the POX starting temperature at which POX starts; the startup control device executes a normal startup POX to raise the temperature of the reformer when the reforming state temperature is equal to or greater than the POX starting temperature and within a POX temperature band below the temperature at which steam reforming is possible; the startup control device executes a normal startup ATR to raise the temperature of the reformer when the reforming state temperature is equal to or greater than the temperature at which steam reforming is possible, and is within the ATR temperature band below a predetermined steady state temperature; and the startup control device executes a normal startup SR when the reforming state temperature is equal to or greater than the predetermined steady-state temperature; characterized in that the startup control device further executes a restart control by the ATR, skipping the normal startup POX, if stop processing by the stop control device is executed in association with stopping of the fuel cell module from a high temperature state, and a restart of operation is executed when the reforming state temperature is within the POX temperature band.