To provide a liquid level detection valve for a fuel tank capable of surely carrying out a switching operation without causing malfunction by correctly detecting the liquid level of a fuel in the fuel tank.

This valve is so composed that a floating body 50 provided with, at its upper end part, a valve head 60 having an upper end surface spherically formed is housed in a nearly cylindrical body 3, and the valve is closed by raising the floating body 50 in conjunction with the rise of the liquid level to abut the upper end face of the valve head 60 on a valve seat 14 formed on the inside surface of the upper wall of the body 3. In this case, a hollow part is formed in the floating body 50 and an air vent window 53 communicating with the hollow part is formed therein.