Turbulent channel flow over a backward-facing step is investigated experimentally under controlled by suction through a slit at the bottom corner of the step. Suction is continuously performed and the direction of suction is perpendicular and horizontal to the main flow. The suction flow ratio is varied from 0.00 to 0.15. The wall static pressure and local heat transfer coefficient are measured behind the backward-facing step. The velocity profiles and turbulent quantities are measured by PIV. It is found that the pressure drop at the step is reduced and the heat transfer coefficient in the recirculating region is improved by suction. The difference of suction direction dose not effect to the heat transfer and fluid flow characteristics.