Single phase specimen of K0.12TiO2 with hollandite-type structure was successfully synthesized by the solid-state reaction under Ar/H2 atomosphere. K+ ions were partially extracted from the parent K0.12TiO2 specimen by the HCl treatment. The K+-extracted K0.08TiO2 specimen worked as a rechargeable electrode material. An initial capacity of 92 mAh/g (cut-off voltage: 1.0 V) could be achieved, which approximately correspond to the composition Li0.28TiO2. A reversible capacity after 50 cycles was about 50 mAh/g.