A thickness detection device, comprising: a plurality of thickness sensors, a transmitting circuit board and a receiving circuit board, and an analyzing module; wherein the plurality of thickness sensors are arranged in two rows in an advancing direction of a sheet medium, and the two rows are arranged in a staggered manner, such that any point on the sheet medium passes through a sensing coverage of the plurality of thickness sensors in the advancing direction; wherein the transmitting circuit board and the receiving circuit board are installed in pair, an advancing channel for the sheet medium is formed between the transmitting circuit board and the receiving circuit board, and the plurality of thickness sensors are installed on the transmitting circuit board and the receiving circuit board; wherein the plurality of thickness sensors comprises transmitting probes and receiving probes, the transmitting probes are installed on the transmitting circuit board, the receiving probes are installed on the receiving circuit board, and the transmitting probes and the receiving probes are installed in a one-to-one correspondence relationship; wherein the transmitting circuit board is configured to control the transmitting probes to transmit a detection signal, which passes through the sheet medium and is received by the receiving probes as a new detection signal; wherein the analyzing module is configured to acquire the new detection signal from the receiving circuit board and perform a signal intensity analysis on the new detection signal, to obtain a thickness of the sheet medium based on a relation between signal intensity and thickness; and wherein the N pairs of transmitting probe and receiving probe are divided into X groups each comprising Y transmitting probes and Y receiving probes, X multiplied by Y is N, the transmitting probes and the receiving probes in a same group perform transmitting operations and receiving operations synchronously, and the X groups of transmitting probes and receiving probes operate in a predetermined group sequence. a plurality of thickness sensors, a transmitting circuit board and a receiving circuit board, and an analyzing module; wherein the plurality of thickness sensors are arranged in two rows in an advancing direction of a sheet medium, and the two rows are arranged in a staggered manner, such that any point on the sheet medium passes through a sensing coverage of the plurality of thickness sensors in the advancing direction; wherein the transmitting circuit board and the receiving circuit board are installed in pair, an advancing channel for the sheet medium is formed between the transmitting circuit board and the receiving circuit board, and the plurality of thickness sensors are installed on the transmitting circuit board and the receiving circuit board; wherein the plurality of thickness sensors comprises transmitting probes and receiving probes, the transmitting probes are installed on the transmitting circuit board, the receiving probes are installed on the receiving circuit board, and the transmitting probes and the receiving probes are installed in a one-to-one correspondence relationship; wherein the transmitting circuit board is configured to control the transmitting probes to transmit a detection signal, which passes through the sheet medium and is received by the receiving probes as a new detection signal; wherein the analyzing module is configured to acquire the new detection signal from the receiving circuit board and perform a signal intensity analysis on the new detection signal, to obtain a thickness of the sheet medium based on a relation between signal intensity and thickness; and wherein the N pairs of transmitting probe and receiving probe are divided into X groups each comprising Y transmitting probes and Y receiving probes, X multiplied by Y is N, the transmitting probes and the receiving probes in a same group perform transmitting operations and receiving operations synchronously, and the X groups of transmitting probes and receiving probes operate in a predetermined group sequence.