An electric current-spin current conversion device according to the invention performs conversion between electric current and spin current utilizing the spin Hall effect or the inverse spin Hall effect of a 5d transition metal. A spin accumulation apparatus according to the invention includes a non-magnetic body in which injected spins are accumulated and an injection unit that injects spins into the non-magnetic body, wherein said injection unit comprises said electric current-spin current conversion device provided on said non-magnetic body, and an electric power source that supplies an electric current to said electric current-spin current conversion device in such a way that a spin current flowing toward said non-magnetic body is generated by the spin Hall effect.