PURPOSE: To attain an appropriate focus control in accordance with the state of a focus distance to a lens or subject in terms of an auto focusing device of a video camera for driving a photographing lens according to the output of a line sensor by rotating the line sensor and providing a line sensor rotating device for rotating the line sensor.

CONSTITUTION: A line sensor 10 cannot transmits focus information to a de- focusing arithmetic circuit 26 under the condition where the line sensor 10 is not applied to a subject. As a result, a focusing failure signal is produced from the de-focusing arithmetic circuit 26, and inputted to a focusing failure detection circuit 29. Then it gives a drive signal to a sensor rotating motor 23 through a sensor rotating circuit 30 to rotate the line sensor 10 through a pinion 24 and a sensor rotating gear 22. The line sensor 10 applies its some part to a subject due to the rotation, and therefore the focus signal is issued to the de-focusing arithmetic circuit 26 from the line sensor 10, thereby carrying out the auto focusing.