To reduce printing irregularity generated by the speed change with time in a printer by simple constitution.

A printing mechanism part 2 for performing printing and a paper feed part 5 for feeding paper 11 are provided. The printing mechanism part 2 has a printing part 3 having a type roller or the like and a platen part 4 for pressing the paper 11 to the type roller through an ink ribbon (not shown in a drawing) and also has an interval signal generating part 9 and a generated interval signal is used as a character signal selecting a type. A DC motor 6 receives power from a power supply part 8. A changeover part 10 for changing over the voltage of the power supply part 8 is provided and judges changeover by the interval signal.