PURPOSE: To enable continuous printing of a round part by rotating it depending on the difference in the speed between a transfer drum rotating at a velocity greater than the peripheral velocity of a main loader and the main loader itself.

CONSTITUTION: A plurality of round parts 1 are arranged at an equi-space on the circumferential surface of a main loader 6 and rotated continuously. The round part 1 taken out with a rotary loader 3 is transferred to the main loader 6. It is shifted roughly by a half circumference, printed with a specified mark by means of a transfer drum 9 and then, transferred to the subsequent process with a chain 8. The transfer drum 9 is rotated at so higher a speed than the main loader 6 that the difference in the speed is created to effect the printing of the mark on the circumference of the part 1. This enables the continuous printing of round parts thereby improving the printing efficiency greatly.