A spot welding inspecting apparatus is provided with: a gun chip; a signal transmitting part; an ultrasonic sensor; an inner cylinder; a through hole; a partitioning cylinder; a first flow path; a second flow path; and a third flow path.The inner cylinder is inserted to an outer cylinder of spot welding gun and holds the ultrasonic sensor. The through hole is provided on the inner cylinder. The partitioning cylinder surrounds the through hole and is inserted into a gap between the ultrasonic sensor and the outer cylinder. The first flow path is formed between the inner cylinder and the partitioning cylinder by passing the through hole from an inner portion of the inner cylinder. The second flow path is formed at the gun chip to be circulated around a front end of the partitioning cylinder. The third flow path is formed between the outer cylinder and the partitioning cylinder. A cooling agent flows in an order of the first flow path, the second flow path and the third flow path.