The invention discloses a method for roundness measurement, which includes the steps of, mounting and rotating an object on a rotary table; driving two measuring surfaces of two measurement units to respectively abut against two opposite sides of the object, wherein the two measurement units are disposed on two opposite sides of the rotary table and the two measuring surfaces are parallel to each other and perpendicular to a to surface of the rotary table; during rotation of the rotary table, measuring intermittently a shortest straight line distance between the two measuring surfaces and generating a variation data and after the rotary table completes a full-circle rotation, a processing unit receiving the variation data and generating measured data. The present invention also discloses a device for roundness measurement.