The thermoplastic Polyoxymethylene (POM) is one of the engineering plastics and it has been used with Glass Fiber Reinforced POM (GFRPOM) in severe environment. It is very important to understand creep behavior that is known as one of visco-elastic behavior in POM and GFRPOM. However, creep behavior of POM is affected by crystallinity because of its high crystalline. Thus, it is considered that influence factors on creep behavior of POM and GFRPOM is crystallinity and fiber content. This research examined the creep behavior using POM and GFRPOM (Vf=2.8%, 8.7%) which adjusted the various degrees of crystallinity by three point bending creep test. As a result, it has been confirmed to be able to adjust the crystallinity of POM and GFRPOM within the range of 5%. On creep behavior, these materials conformed to Arrhenius type of time-temperature superposition principle. And master curve can be drawn by superposing the creep compliance curves of each test temperature. When the master curves of all materials were compared, creep behavior was suppressed with crystallinity and fiber volume fraction increasing.