The behavior of ultraviolet (UV) curable resin in the initial stage of curing was investigated using a particle image velocimetry (PIV) technique. The specimen consisted of a mold and UV curing resin in liquid form with acrylic powder. The mold consisted of glass and acrylic plates. The specimen was illuminated with UV rays downwards from the upper side of the specimen. The images of the resin during curing process were then captured at a constant time interval using a digital camera. The results indicated that the behavior of uncured resin during initial curing occurred in the upper part of the resin, and the behavior of the uncured resin in the initial cured stage determined the behavior of the resin after the initial stage.