[en] We have investigated the effect of removal thickness with electropolishing (EP) using our first fabricated L-band bulk-niobium single cell cavity(SHI-1). We obtained finally the maximum accelerating field (max Eacc) of 32 MV/m, by the removed thickness of 150 μm, which included 20 μm light chemical polishing (CP) and 750degC annealing. With this result, we have fabricated a second single cell cavity (SHI-3) applying 130 μm CP, then 30 μm EP on the cavity. And the cavity was not annealed because of checking Q-degradation. We could not obtain a good performance (the max Eacc was 7.3 MV/m) due to bad welding condition on equator section. However, the cavity without annealing gave us the result where Q-degradation was not observed. Next, we fabricated a 3-cell cavity with welding condition on SHI-3. In this paper, we report on the result, 3-cell cavity design and performance. (author)