PURPOSE: To reduce the resistance of lever operation by forming the diameter of a spherical valve body with respect to the inside diameters of valve seats which cooperate with the valve body in a cock body to be in a defined range.

CONSTITUTION: A lever member 5 is rotatingly operated to switch over the connection/disconnection among a main fuel inlet passage 14, an inside passage 11 as a reserved fuel inlet passage, and a fuel outlet passage 27 which are formed on a cock body 2. The ratios of the diameter of a valve body 4 to the inside diameters of a recessed portion 29 and annular seal members 33, 34 are defined as 1.15W1.70. Thereby, a favorably fitting feeling can be obtained at the time of engaging the valve body 4 with the recessed portion 29 and both passage openings 22, 28 during the rotating operation of the lever member 5.