To obtain a self-propelled spraying machine having a tank, an engine, a pump and a spraying nozzle mounted on a crawler-type mobile body and capable of continuing the spray work over a long period by increasing the capacity of the tank while keeping the compactness of the machine body.

The height of the upper face of a mobile frame 1 having crawler-type driving gears at the right and the left is made to be lower than the top of the crawler belts 5, 5. A front tank-holding frame 6 and a rear tank- holding frame 7 are placed at the front and rear sides on the upper surface of the mobile frame. A downward protrusion 12a is formed on the bottom of a tank 12. The bottom of the tank 12 is placed by fitting the tank along the front and rear tank-holding frames 6, 7 in such a manner as to insert the downward protrusion 12a into a space encircled with the crawler belts 5, 5 and the mobile frame 1.