Glycidol polymerized by the microbial resting cells and commercially available hydrolase enzyme having epoxide hydrolase activity without added water produced the water-soluble poly(glycidol). As a typical example, a mixture of glycidol and 5% lipase AK (Pseudomonas fluorescens) was stirred at 30 degreesC for 3 d to produce the poly(glycidol) with a weight-average molecular weight of 900.