An objective image quality assessment device of a video quality for estimating a subjective image quality from compressed bit stream is provided. The device includes a macro-block layer parameter analyzer for acquiring a quantizer scale size defined with respect to each macro-block and a coding type of a slice from a compressed bit stream, an orthogonal transformation coefficient in each macro-block, and a reference frame number in the macro-block applied with a motion compensating prediction, an average quantizer scale calculator for obtaining an average in a sequence of the quantizer scale size for every coding type of the slice, a spatial degradation feature calculator and a temporal degradation feature calculator for obtaining a spatial degradation feature and a temporal degradation feature, in each macro-block, and an image feature integrator for deriving the objective image quality based on the features obtained in the calculators.