To propose a tank truck wherein first need of an explosionproof structure is eliminated so that the truck is excellent in terms of cost, second a sensor is excellent in durability to lengthen a service life, less failure occurs, and maintenance is facilitated as well, and third an overflow when loading can be reliably prevented.

The tank truck 1 for loading and carrying a liquid A such as an oil as a dangerous substance has the inside sectioned into a plurality of tank chambers 4 and includes a sensor 34 for generating and receiving ultrasonic waves attached on an external surface 36 of a tank wall 25 made of aluminum or iron under a protective frame 3. With received reflection waves attenuated, whether the liquid A loaded into the tank chambers 4 has exceeded the maximum allowable carrying capacity is determined. Further based on the determination, a control valve to an air pipe to a pneumatically opened/ closed bottom valve of the tank chamber 4 is controlled to open/close, or a pump or an open/close valve on a side of a loading facility is controlled to drive or to open/close.