To provide an ignition timing control device and an ignition timing control system capable of sufficiently enhancing the output efficiency of an internal combustion engine according to an opening of a tumble control valve (TCV) even if the tumble control valve is controlled to an intermediate opening.

When a TCV is operated in the intermediate opening, ignition timing is set to timing retarded from base ignition timing used for fully opening the valve (S40 and S50). Thus, it is possible to prevent a trouble that the pressure peak timing of a combustion chamber becomes earlier than optimum timing (e.g., ATDC20CA). Further, the ignition timing is retarded as the intermediate opening of the TCV 31 is delayed (near fully closed) (S40 and S50). Thus, it is possible to prevent a problem that pressure peak timing is more delayed than the optimum timing. Consequently, because the base ignition timing is corrected according to the intermediate opening, it is possible to sufficiently enhance the output efficiency of the engine.