A car safety seat includes a seat body, at least one knob and at least one safety belt. The seat body has at least one slot structure. The slot structure includes a plurality of first positioning slots and a plurality of guiding slots. Each of the first positioning slots is connected with another adjacent one of the first positioning slots through one of the guiding slots. The knob is movably disposed on the seat body and has a second positioning slot. The safety belt penetrates through the second positioning slot and the corresponding first positioning slot in sequence. The knob is adapted to rotate to drive the safety belt to enter the corresponding guiding slot, and the knob is adapted to move along the slot structure to drive the safety belt to pass through the guiding slot to arrive another adjacent one of the first positioning slots. |