A multi-inclined anvil structure for a stapler has a body, an operating portion and a flattening surface. The body has a horizontal imaginary plane. The operating portion is recessed downward in the top of the body and has a projection plane that has a narrow front and a wide rear. The flattening surface is formed in a bottom surface of the operating portion and has two inclined bottom portions. Each inclined bottom portion is inclined and has a high front and a low rear relative to the horizontal imaginary plane. An inclined bottom angle is formed between an extension direction of the inclined bottom portions and the horizontal imaginary plane. When the stapler is applied to staple a few sheets of paper, a staple-sliding problem can be resolved. When the stapler is applied to staple many sheets of paper, a well-clinched quality can be provided.