When a CPU receives an input signal that selects an operation mode through an operation mode selecting screen, the CPU determines whether or not the selected operation mode coincides with an operation mode stored in individual operation mode histories of an main body NVM. If both the operation modes do not coincide with each other, the CPU starts counting of a midway consumption of a toner representing the consumption of the toner used thereafter. Further, the CPU determines whether or not the count of the midway consumption arrives at a specified value. If the count arrives at the specified value, the CPU updates the individual operation mode histories of the main body NVM with the selected operation mode, and switches an existing operation mode to the selected operation mode.