To solve the problem of increase of a treatment time to crush and dry a food treated-object, as the food treated-object including much starch and water transforms to sticky paste when starch and water are slowly heated while stirred, and lumps by collecting together, thus it is hard to dry the inside of the lump.

The treated object is stirred, crushed and dried while jetting a heating gas of 100C or more into a treatment tank 12 comprising a treated-object charging port 18, a treated-object discharge port 20 and a stirring device for stirring the charged treated-object. A surface of the starch included in the treated object is rapidly dried before it largely lumps. When the lump is crushed by being stirred by the stirring device, the sticky paste-like starch is exposed from the inside of the lump. The sticky paste-like starch is also rapidly dried. Thus the lump is gradually reduced in size, and promptly dried to be powder.