To ascertain the relation between the infiltration rate, cover material and hydraulic conductivity of forest soils in Japanese cedar (Cryptomeria japonica) and Hiba arborvitae (Thujopsis dolabrata) plantations, we conducted artificial rainfall experiments using an oscillating nozzle rainfall simulator. The maximum infiltration rate (FIR_max) was higher than that found in previous studies of cypress plantations. Especially in conditions where surface cover materials are less than 1000 g/m², FIR_max tends to become higher than the value of the cypress forest in several magnitudes. FIR_max showed over 100 mm/h, irrespective of the amount of surface cover materials. The result confirmed little or no correlation between FIR_max and surface cover materials in either of the studied tree species. FIR_max were lower than hydraulic conductivity. FIR_max showed no correlation with hydraulic conductivity and fine fraction content. Therefore, the differences of FIR_max in cedar and hiba plantation were not explainable by surface cover materials, hydraulic conductivity, or the fine soil fraction content, which contrasts with results of previous studies of cypress plantations.