A piercing mechanism of a bread maker suitable for disposing within a housing of a bread maker and configured to pierce a sealing film of a bread ingredient box, said piercing mechanism comprising: a bottom seat; a top seat disposed above said bottom seat and including a support portion for supporting the bread ingredient box; a plurality of spaced-apart support units disposed on said bottom seat and connected to and supporting said top seat, each of said support units including an outer support tube extending upward from said bottom seat, an inner post inserted into said outer support tube and extending out of said bottom seat for abutting against the housing, an outer spring sleeved on said outer support tube and having two opposite ends respectively abutting against said top seat and said bottom seat, and an inner spring sleeved on said inner post and having two opposite ends respectively abutting against said inner post and said outer support tube; and a sawtooth blade disposed on an inner side of said bottom seat and including a plurality of teeth arranged on a top periphery thereof; wherein said piercing mechanism is movable between a non-piercing state and a piercing state; wherein, said teeth of said sawtooth blade is located lower than said support portion when said piercing mechanism is in the non-piercing state, and extend into an inner side of said top seat higher than said support portion when said piercing mechanism is in the piercing state for piercing the sealing film of the bread ingredient box; wherein said top seat is movable relative to said bottom seat when said piercing mechanism is in the piercing state; wherein said outer spring is uncompressed when said piercing mechanism is in the non-piercing state, and is compressed by said top and bottom seats (7, 3) when said piercing mechanism is in the piercing state, said inner spring being compressed by said inner post and said outer support tube when said piercing mechanism is in the non-piercing and piercing states. a bottom seat; a top seat disposed above said bottom seat and including a support portion for supporting the bread ingredient box; a plurality of spaced-apart support units disposed on said bottom seat and connected to and supporting said top seat, each of said support units including an outer support tube extending upward from said bottom seat, an inner post inserted into said outer support tube and extending out of said bottom seat for abutting against the housing, an outer spring sleeved on said outer support tube and having two opposite ends respectively abutting against said top seat and said bottom seat, and an inner spring sleeved on said inner post and having two opposite ends respectively abutting against said inner post and said outer support tube; and a sawtooth blade disposed on an inner side of said bottom seat and including a plurality of teeth arranged on a top periphery thereof; wherein said piercing mechanism is movable between a non-piercing state and a piercing state; wherein, said teeth of said sawtooth blade is located lower than said support portion when said piercing mechanism is in the non-piercing state, and extend into an inner side of said top seat higher than said support portion when said piercing mechanism is in the piercing state for piercing the sealing film of the bread ingredient box; wherein said top seat is movable relative to said bottom seat when said piercing mechanism is in the piercing state; wherein said outer spring is uncompressed when said piercing mechanism is in the non-piercing state, and is compressed by said top and bottom seats (7, 3) when said piercing mechanism is in the piercing state, said inner spring being compressed by said inner post and said outer support tube when said piercing mechanism is in the non-piercing and piercing states.