1. An objective image quality assessment device of a video quality for estimating a subjective image quality of a video without using a reference image, the objective image quality assessment device comprising: a macro-block layer parameter analyzer for acquiring at least a quantizer scale size defined with respect to each macro-block and a coding type of a slice to which each macro-block belongs from a compressed bit stream; an average quantizer scale calculator for obtaining an average in a sequence of the quantizer scale size for every coding type of the slice; and an objective image quality deriving section for deriving the objective image quality with the average in the sequence of the quantizer scale size obtained by the average quantizer scale calculator as a feature, wherein the subjective image quality is estimated using only the compressed bit stream.