PURPOSE: To produce smoothly a beltlike expanded food, by injecting a liquid into a food material fed into an inner cylinder, kneading the resultant mixture, and heating the mixture while advancing the food material with plural screws.

CONSTITUTION: A food material 3, e.g. meat, rice, starch or ground fish meat, is fed through a branch inlet channel 4l into an inner cylinder 2 placed in the interior of an outer cylinder 1, advanced with a pair of rotating shafts 8 having trapezoidal wide screws 9, heated with water flowing through a coiled pipe 12 arranged between the outer cylinder 1 and the inner cylinder 2, and then fed into R-shaped screws 10 of medium width having a narrow valley width following the screws 9. A liquid, e.g. water, is injected from an injection channel 5 into the material 3, and kneading and addition of water are carried out. The resultant material is then fed to a part of screws 11 of small width, kneaded, suitably pressurized and then extruded from a discharge outlet as an unexpanded beltlike material.