A 1/50 scale model of side tanks of a tanker is used in this experiment to know effects of rolling on the heat transfer from shell walls. Results of the experiment are as follow. (1) The temperature of oil in the tank becomes uniforrn when rolling occurs. (2) The heat transfer coefficient increases almost linear according to the angle and frequency of rolling. (3) Fin effect of stiffeners is little, then their size and material affects little the heat transfer from stiffeners. They work mainly as mixers of oil in tanks. Empirical equations for increments in the heat transfer coefficient by rolling are given as, Δ N_u =0.0160 R_e ^0.942 P_r ^1/3……for side shell Δ N_u =0.0155 R_e ^0.910 P_r ^1/3……for bottom shell where Δ N _u=Δα l /λ and R_e =2π b θ l / ( T ν). (Δα : increment in heat transfer coefficient, l : stiffener space, λ : thermal conductivity, θ : rolling angle, b : half breadth of tank, T : rolling period, ν : kinematic viscosity.)