Three-dimensional ultrasound microscopy with the central frequency of 120 MHz made it possible to observe in vivo sebaceous glands at the deep part of the dermis at microscopic level. The deformation displacements were measured by an established testing device, and the viscoelasticity was estimated from the measured displacements and Voigt model. The occupancy, density or average size of sebaceous glands was compared with the viscoleasticity. There were three major findings in the comparisons. First, the occupancy of sebaceous gland showed negative correlation with the elasticity. Second, the density of sebaceous glands showed positive correlation with the viscosity. Third, the average size of sebaceous glands showed negative correlation with the viscosity. In conclusion, viscoelastic property of human skin is strongly influenced by the morphology of the sebaceous glands.