A vibration sensor is designed to have a pressure-enhancing member, a pressure sensing device and first, second, third chambers. An air gap is designed to enable the first chamber to be vented to the third chamber such that the first chamber is combined with the third chamber to obtain a communicable air volume. An adhesive layer is formed between a spacer and a circuit board, and the air gap is formed in an adhesive-absent section between the spacer and the circuit board. When the pressure-enhancing member is moved to squeeze the air in the second chamber, a sensitivity of the pressure sensing device will be greatly improved.