A method for detecting a crater end of a continuously cast product including installing an ultrasonic shear wave sensor for transmitting an ultrasonic shear wave to a cast product and receiving the transmitted ultrasonic longitudinal wave and an ultrasonic longitudinal wave sensor for transmitting an ultrasonic longitudinal wave to the cast product and receiving the transmitted ultrasonic longitudinal wave at the same position in a continuous casting machine or at positions apart from each other in a casting direction, but at the same position in a transverse direction of the cast product, detecting based on variations of an ultrasonic signal received by the ultrasonic shear wave sensor that the crater end of the cast product is matched with the installed position of the ultrasonic shear wave sensor, calibrating a calculation formula for determining the crater end and determining the crater end.