This manual change-over valve is a rotary valve type 3-position 4-port valve which changes the running direction of hydraulic oil by operating a handle knob. The rotary valve and valve seat are sealed positively by grinding and oil leaking is practically zero. Incorporation of a detent mechanism results in keeping the change-over position positively. As a handle knob operation system is adopted, the change-over position is not moved carelessly, resulting in assurance of safety