The number and head direction of Liriomyza trifolii (Burgess) caught on yellow sticky traps in tomato greenhouse were investigated for 8 weeks to find a flight pattern in tomato greenhouse. The traps were rolled into a cylindrical shape and placed just above the plant canopy level throughout this study. The greenhouse was 5,000m² (50m x 100m), and each trap was located every 5m in width and length (11 x 19). The trap (14.8cm x 9.5cm) was equally divided horizontally into upper, middle, lower sections. On each trap, head direction of individual leafminer was decided among three distinctive positions (upward, neutral, and downward). Proportion of the total caught leafminers was highest in upper section (79%) compared to middle (12%) and lower (9%) sections throughout the entire sampling period. In the upper section of the sticky trap, 51% of the leafminers were headed downward compared to neutral (36%) and upward (13%). In the middle section, 25% of the leafminers were downward compared to neutral (40%) and upward (35%). In the lower section, 29% of the leafminers were downward compared to neutral (36%) and upward (35%). These results show significantly high proportion of the downward leafminers in the upper section of the sticky trap compared to other sections. In conclusion, a large number of downward leafminers in upper section of the sticky trap suggest that the general flight course of leafminers in tomato greenhouse would be from the top of the plant canopy to the lower parts of the plant.