A material testing machine measuring strain of a tube-like test piece, comprising: a plurality of radial direction displacement detection units; an axis direction displacement detection unit; and a calculation unit that calculates the strain, wherein: each of first and second displacement meters of at least one of the radial direction displacement detection units comprises: a needle; a fixed frame; a movable frame; and a displacement sensor having a body part and a contact protruding from the body part, and wherein a tip of the contact contacts a stopper plate; the needle is oriented in the radial direction of the test piece; the needle protrudes from an end of the movable frame; displacement in the radial direction of the test piece is detected by detecting a moving amount of the needle; and the calculation unit calculates a curvature radius in the tube axis direction of the test piece.