Polymer microfluidic devices are used for many purposes such as microarrays and biochips. The key tool for manufacturing these chips in bulk is an appropriate mold. However, the popular material for making molds is nickel or nickel alloys, which have low stiffness and wear out easily. Zr-based metallic glass is a promising material for micro- or nanomolds because it has good mechanical properties and can be easily formed with high precision. In this paper, Zr-based metallic glass is proposed for use as micromold insert to make poly-(methyl methacrylate) (PMMA) microfluidic devices. Our experiments show that they have good feature integrity and replication quality. Microchannels we fabricated using these replicas did not leak and had good flow performance. Zr-based metallic glass can greatly ease the manufacture of plastic microfluidic devices for research and commercial applications.