The present invention relates to a wholly aromatic polyester carbonate and a process for its production. An aromatic dicarboxylic acid, an aromatic diol, and a diaryl carbonate are used as starting materials in specific molar ratios, a prepolymerization step, a crystallization step, and a solid-phase polymerization step are essential steps, and a compression molding step is an optional step. This makes it possible to produce with good productivity a wholly aromatic polyester carbonate that has low coloration and a high degree of polymerization.