The present invention provides a thermal printer capable of printing by selecting a desired print density, and a print density adjustment method thereof. The thermal printer includes a thermal head having a heat generating element as a heat source and a printer control section. The printer control section corresponds to the initial power applied to the heat generating element of the thermal head according to the number of print density levels. The difference between the time and the maximum energization time of the heating element is divided to calculate the energization correction time, the energization correction time is increased/decreased at the initial energization time to set the energization time for each print density level, and the energization at each print density level is performed. The current is applied to the heating element at a time, and printing is performed using the print pattern. The thermal recording paper on which test printing has been performed is discharged from the paper outlet, and the user can refer to the thermal paper after the test printing and set a desired print density level using the print density level selection screen displayed on the display unit.