A tire testing apparatus of a drum type, comprising: 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, the tire being attached to a tire shaft; 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, thereby acquiring image information of the ground contact surface of the entire circumference or part of the tire, the image information being the imaged ground contact surface of the tire at every angle θ T of the tire shaft; an edging processing unit that performs edging processing of the image information of the imaged ground contact surface of the tire; a division processing unit that performs division processing of 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, wherein the matching processing unit adopts, as a template, one of the regions divided by the division processing unit, and performs matching processing for matching the region of the template and the image information of the ground contact surface of the tire with each other, the image information being matched is subjected to the edging processing at a different time from the divided region of the template,; and a slip amount calculation processing unit that calculates a slip amount by using a result of the matching processing and a ground contact surface moving amount generated by a rotation amount of the drum, wherein the ground contact surface moving amount represents a differential time multiplied by a speed of the drum. 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, the tire being attached to a tire shaft; 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, thereby acquiring image information of the ground contact surface of the entire circumference or part of the tire, the image information being the imaged ground contact surface of the tire at every angle θ T of the tire shaft; an edging processing unit that performs edging processing of the image information of the imaged ground contact surface of the tire; a division processing unit that performs division processing of 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, wherein the matching processing unit adopts, as a template, one of the regions divided by the division processing unit, and performs matching processing for matching the region of the template and the image information of the ground contact surface of the tire with each other, the image information being matched is subjected to the edging processing at a different time from the divided region of the template,; and a slip amount calculation processing unit that calculates a slip amount by using a result of the matching processing and a ground contact surface moving amount generated by a rotation amount of the drum, wherein the ground contact surface moving amount represents a differential time multiplied by a speed of the drum.