An object is to provide a method and apparatus for extending a base-side portion of croissant dough in an approximately triangular shape toward the right and left largely. A method of extending food dough (1) in an approximately triangular shape includes the steps of opening a slit (S) formed in a central portion of the base of the food dough (1), extending base-side portions on both sides of the opened slit (S) outward in opposite directions, and extending a top-side portion of the food dough (1) toward a top thereof. An apparatus includes a slit opener (5) including a pair of dough holders (5L, 5R) being movable away from each other while holding the food dough (1) at both side portions of a slit formed in a central portion of the base of the food dough in the triangular shape, a first extender (7) including a pair of extending rollers (103L, 103R) being movable outward in opposite directions, respectively, while pressing base-side portions on both sides of the slit (S) opened by the slit opener (5), and a second extender (9) configured to extend a top-side portion of the triangular shape, located from a vicinity of the portions extended by the first extender (7), toward the top of the food dough (1).