PURPOSE: To easily measure the out-of-and in-plane movement of an object to be measured with nearly the same resolution by Setting the surface of the object to be measured and surfaces of speckle pattern movement detecting means in such a relations that the images of swinging and tilting planes can be formed.

CONSTITUTION: The light from a coherent light source 1 irradiates an object 31 to be measured through a lighting lens 2. The object 31 and speckle pattern movement detecting means 51 and 52 are set in such a relation that the images of swinging and tilting planes can be formed and lenses 41 and 42 form the images of the planes. When the object 31 makes out-of-and in-plane movement, the moving direction of the object 31 can be detected from the outputs of the detecting means 51 and 52, because a speckle pattern moves on the detecting surface of the detecting means 51 and 52. In other words, when the difference between and sum of the moving amounts of the speckle pattern detected by the detecting means 51 and 52 are calculated 7, the moving amount of the object 31 in the out-of-plane (Z) direction and in-plane (X) direction can be measured. Therefore, the out-of-plane movement of the object 31 can be measured with nearly the same resolution of the in-plane movement.