To obtain a compact and inexpensive level gauge which can sense when an automobile tire goes flat or bursts, by putting water in a bat-shaped container, fitting electrodes at ends of right and left wings and fixing the container in the vicinity of the tire.

A water 3 is put in a bat-shaped container, and electrodes 2 are fitted at ends of right and left wings. The container is fixed in the vicinity of a tire. A side of the water container is inclined by approximately 5mm to prevent waves generated at a water surface when the road is bad from flowing to the opposite electrode. The device can be a single wing type with only one wing rendered usable. In this case, the vane may be fitted at any of the right and left sides and components of the level gauge can be compact in size.