A cutter includes a rotary shaft having a longitudinal axis and a plurality of circumferentially spaced-apart multi-blade cutting strips each of which includes a plurality of cutting blades spacedly provided at at least one longitudinal side edge of a cutting strip body thereof. Each cutting blade of each cutting strip has a portion (P1) staggered with respect to an adjacent cutting blade of an adjacent cutting strip along a circumferential direction around the longitudinal axis, and a remaining portion (P2) aligned with the adjacent cutting blade of the adjacent cutting strip along the circumferential direction. The portion (P1) has an offset length (D) measured along the longitudinal direction.