PURPOSE: To record a digging process and a correcting process on the same recording paper in different colors by canceling the quantity of upward movement pulses with the quantity of downward movement pulses, and changing recording colors only when a cancel signal is received.

CONSTITUTION: When the digging process advances to, for example, a point A of depth l1 from the ground surface H and then increases in inclination, a digging machine 1 enters a return process wherein it moves up to a point B of depth l5 having no inclination and then begins to perform the correcting process. The paper is fed in proportion to downward movement pulses 8a at the time of the downward movement of a rope 2 and record in, for example, blue is drawn. The paper is not fed in the return process, so the recording is stopped and the quantity of upward movement pulses 8b is stored by a cancel detecting circuit 66. The quantity of downward pulses 8a is supplied to the cancel detecting circuit 66 in the correcting process simultaneously with paper refeeding operation to cancel the recording quantity of upward movement pulses 8b. The cancel signal is generated during said period to change recording colors of a recording pen.