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We fabricated single-electron transistors (SETs) with ferromagnetic (FM) Co leads and superconducting (SC) Al islands, and measured their tunnel magnetoresistances. Under the antiparallel magnetization state of the two FM leads, current increase due to the SC gap suppression by spin accumulation was observed. Tunnel magnetoresistance ratios of the antiparallel state to the parallel state were investigated for 10 FM SETs with different spacings between the two FM leads, from 0.35 to 50 mm. Spin valve effects were confirmed in the SETs with an FM lead spacing not only on the submicron order but also of 50 mm.

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