V-groove device was fabricated for precision coupling of planar optical splitter and optical fibers. V-groove was made through select wet etching of Si wafer by using KOH solution. Etching rate and surface roughness were checked, changing KOH composition(10, 20, 30, 33, 40 wt.%) and etching temperature (50, 60, 70, $80^{circ}C$) to fabricate V-groove device effectively. Etching rate was the fastest as $1.84;{mu}m/min$ in case of etching by 20 wt.% KOH on $80^{circ}C$, surface roughness was the best in case of etching by 33 wt. % KOH on $80^{circ}C$.