We clarified the disease pathophysiology caused by Eustachian tube disfunction by examining the difference in each age of the Eustachian tube form. We measured the living human Eustachian tube using multislice CT (MSCT). Comparing without skew or contraction in case of cadaveric spesimens the length of each part of the Eustachian tube, the diameter, and the angle based on the image data obtained by MSCT for all age groups in our study, which involved 48 samples from adults and 31 from chidren (23 ears under 7 years old). We classified specimens from those less than 6 years old as the infant-youngchildren group, and from those 7 years or older as the schoolchildren-adult group. Mean total length, cartilage part length, and bony part length was, as expected, longer in schoolchildren-adult group than infant-youngchildren group, as was the pharyngeal orifice diameter. The mean angle between the bony part and cartilage part was more acute in schoolchildren-adult group, as was the cartilage part steepness. We proved a characteristic of three-dimensional anatomy of a child Eustachian tube in living human organism.