PURPOSE: To raise the efficiency of excavating operations by a method in which the movement of marks provided in place of a working machine is photographed by a television camera to obtain the locus of operations, and the locus of operations, together with target position of excavation, is displayed on the monitor television of an operation room.

CONSTITUTION: Marks M1 and M2 are provided on the pivotal connection of the boom 3 and arm 4 of a working machine, e.g., power shovel and also on the pivotal support of the rod of an arm cylinder 5. A television camera is set near an excavation site by the excavating working machine to take the photograph of the movement of the marks M1 and M2, and picture signals from the television camera 1 are arithmetically processed to obtain the operational locus of the working machine. The operational locus so obtained and target position of excavation are displayed on a monitor television 22 in an operation room. While monitoring the excavating conditions by an operator, highly efficient excavating operations can thus be performed.