A tire testing apparatus of a drum type includes: a drum including a transmission portion on an outer circumferential surface; an imaging device that images a ground contact surface of a tire from an inside of the drum via the transmission portion; a ground contact surface imaging processing unit that images, using the imaging device, the ground contact surface when the tire is brought into ground contact with the transmission portion; an edging processing unit that performs edging processing for image information of the imaged ground contact surface of the tire; a division processing unit that performs division processing for the image information subjected to the edging processing into regions which satisfy a predetermined resolution condition; a matching processing unit that performs matching processing by using the divided regions; and a slip amount calculation processing unit that calculates a slip amount and a ground contact surface moving amount.