Monitoring of moisture content by an infrared (IR) moisture sensor during fluidized bed granulation is a necessary way to control granule growth; however, this method requires prior investigation of IR absorption characteristics indicating the relationship between granule moisture content and IR absorption. In this contribution, for a better understanding of this IR absorption characteristics, fluidized bed granulation and drying were conducted at various powder samples and operating conditions with monitoring of moisture content by an IR moisture sensor. The effects of powder properties such as water absorbing potential and diameter on the IR absorption characteristics were investigated experimentally. Based on the results obtained, the water transfer mechanism among particles was analyzed, and factors which determined the IR absorption characteristic during fluidized bed granulation and drying were discussed.