A novel polycarbonate diol is useful as a raw material for producing a polycarbonate diol-based polyurethane with a high degree of hardness, superior abrasion resistance, and superior hydrophilicity. The polyurethane is useful in paints, coating agents, synthetic leathers, artificial leathers, and highly-functional elastomers, or the like. The polycarbonate diol is also useful for producing an active-energy radiation curable polymer composition giving a cured film having superior contamination resistance and high degree of hardness. The curable polymer composition contains a urethane(meth)acrylate oligomer obtained from the polycarbonate diol. The polycarbonate diol is obtained, for example, by reacting two specific types of diols with diester carbonate in the presence of a transesterification catalyst. The catalyst has a metal of Group 1 or 2 on the periodic table. A metal content of the transesterification catalyst is 100 weight ppm or less.