An onboard LH-2 tank for a liquid hydrogen car must have small size, light weight and low evaporation loss of hydrogen. Among these the reduction of evaporation loss is especially crucial for the hydrogen car developed at the Musashi Institute of Technology, because a LH-2 PUMP is inserted into its LH-2 tank and the pump turns out to be a major path for heat inflow to the tank. Presented in this paper are discussions on countermeasures against the aforementioned problems by investigation of the structure of the LH-2 pump and pump space.