Posit number system has been recently widely applied in many fields of applications. For different applications, the precision requirements are usually different. In addition, the transprecision computing paradigm, which is proposed for energy efficient computation, even requires different precision in each computation step. To support computations of various precision in a single hardware architecture, in this paper, a unified architecture of multiple-precision posit multiplier is proposed. The proposed posit multiplier supports the commonly used Posit(8, 0), Posit(16, 1), and Posit(32, 2) formats, where one Posit(32, 2), or two parallel Posit(16, 1), or four parallel Posit(8, 0) multiplications can be accomplished each time. Each module of the proposed posit multiplier is carefully tailored for resource sharing among three supported precision formats. Compared to the Posit(32, 2) multiplier, the proposed multipleprecision multiplier adds the support for parallel low-precision posit multiplications with only 12.8% more area and 15.4% more power. The proposed architecture can be used in posit-enabled general-purpose processor designs.