Provided are a material testing machine that can improve the responsiveness and the stability and perform a feedback control for a test condition, and a method for controlling a material testing machine. A monitor amount conversion unit (23) calculates an estimation testing force by multiplying an elongation amount measured by an elongation amount measurement unit (22) by a control stiffness of a test piece (TP). A material test control unit (24) determines an operation amount for a servo motor (43) for reducing a deviation between an actual testing force applied to the test piece (TP) and a target testing force according to a test condition based on an estimation testing force, and executes a tensile test for the test piece (TP).