A spindle vibration measuring system which measures vibration of a spindle in a machining device that performs a cutting or abrading process on a workpiece. The machining device has a workpiece holder that holds the workpiece, the spindle that holds a tool, and a moving mechanism that relatively moves the workpiece holder and the spindle. The spindle vibration measuring system acquires positional variation data or vibration data of the moving mechanism when the spindle rotates, and a result related to vibration of the spindle to output or store based on the positional variation data or the vibration data.