Dense hairs on leaf surfaces hinder predatory mites from foraging for prey and, thus, potentially alleviate predation risk in sympatric mite herbivores. In our previous laboratory experiments using leaf discs, eggs of herbivorous Brevipalpus obovatus (Tenuipalpidae) were less consumed by a predator Phytoseius nipponicus (Phytoseiidae) on the abaxial leaf surface (more hairy) than on the adaxial surface (less hairy) of Viburnum erosum var. punctatum (VEP; Adoxaceae). However, 35% of B. obovatus eggs was laid on adaxial leaf surfaces (=upper side) of VEP in the field study. Therefore, we hypothesized that difference in the gravity direction on the leaf surfaces also affected predation efficiency, and examined the interaction between gravity (upper/lower) and surface structures (adaxial/abaxial) using setup that both sides of VEP leaves were available for mites. As a result, P. nipponicus adults notably preferred the lower and abaxial leaf surface. In contrast, B. obovatus adults preferred the upper and adaxial surface. Such opposite preference suggest that B. obovatus eggs on the upper side of a VEP leaf are less frequently predated than that on the lower side regardless of leaf-surface structures. We conclude that the gravity effects reduce the predation risk of B. obovatus eggs on the upper (adaxial) leaf surface of VEP.