The irreversible thermodynamics of viscous solids with microstructures is developed in a new approach. In this general theory, the ’’particle’’ in the continuous medium is a composite ’’molecule.’’ The field equations describing the motions of the mass points making up the molecule are written down in terms of an internal energy potentialUand a dissipation functionD. The irreversible mechanical force acting on the mass point is related toD. The conservation laws of momentum, energy, and angular momentum are derived from the spatial invariance properties ofUandD, and are thus automatically satisfied. The balance of entropy is a built‐in process. The cases of anisotropic liquids and liquid crystals can be developed in a similar fashion.