The efficiency of a pheromone trap was evaluated as an alternative to the “sweeping method” that has been established as a monitoring method of the rice leaf bug, Trigonotylus caelestialium. A sticky trap, a plate with sticky surfaces on both sides, was used and a rubber septum impregnated with 0.01 mg of the synthetic sex pheromone was placed at the center of the upper side of the plate. The sticky traps were installed in paddy fields in Joetsu and Nagaoka, Niigata Prefecture and Toyama, Toyama Prefecture. The most effective trap height was estimated to be near the canopy of rice plants; therefore, the sticky trap was placed by poles at the height of the canopy in the center of a paddy field, and the traps were checked every day throughout the growing season in 2005. Monitoring by means of the sweeping method was also performed in the same fields at approximately five-day intervals. The number of adults captured by sweeping increased from the middle of June to early or mid-July, and then decreased, irrespective of region or rice variety, and the adults increased again at the heading time of each rice variety. The fluctuation pattern of males caught in traps and the number of males captured by sweeping were roughly synchronized in each paddy field. This result suggests that the pheromone trap can be utilized as a monitoring tool for the rice leaf bugs in paddy fields.