An amplifier-embedded pressure sensor, which is connected to a pipe including a fluid passage, comprising: a pressure-detecting unit which has a pressure-receiving surface in contact with a fluid flowing in from the pipe, and which detects a differential pressure between the fluid in contact with the pressure-receiving surface and a space where the pipe is installed and outputs a pressure signal; an amplifier circuit board which has an amplifier circuit for amplifying the pressure signal detected by the pressure-detecting unit ; a housing to which the pressure-detecting unit is fixed; and a separation part which is fixed to the housing and separates a space inside the housing into a first space (R1) where the pressure-detecting unit is disposed and a second space (R2) where the amplifier circuit board is disposed, wherein the housing includes an inflow port for letting cooling gas for cooling the amplifier circuit board flow into the second space (R2) and a discharge port for discharging the cooling gas from the second space (R2), an external wire for transmitting the pressure signal amplified by the amplifier circuit to an external device, a coupling part to which the external wire is coupled, characterized in that the amplifier embedded pressure sensor further comprises: a cladding part cladding the external wire ; wherein the first space (R1) communicates with a space near the external device through a third space (R3) between the external wire and the cladding part for allowing the gas in the space near the external device to be supplied to the first space (R1). a pressure-detecting unit which has a pressure-receiving surface in contact with a fluid flowing in from the pipe, and which detects a differential pressure between the fluid in contact with the pressure-receiving surface and a space where the pipe is installed and outputs a pressure signal; an amplifier circuit board which has an amplifier circuit for amplifying the pressure signal detected by the pressure-detecting unit ; a housing to which the pressure-detecting unit is fixed; and a separation part which is fixed to the housing and separates a space inside the housing into a first space (R1) where the pressure-detecting unit is disposed and a second space (R2) where the amplifier circuit board is disposed, wherein the housing includes an inflow port for letting cooling gas for cooling the amplifier circuit board flow into the second space (R2) and a discharge port for discharging the cooling gas from the second space (R2), an external wire for transmitting the pressure signal amplified by the amplifier circuit to an external device, a coupling part to which the external wire is coupled, characterized in that the amplifier embedded pressure sensor further comprises: a cladding part cladding the external wire ; wherein the first space (R1) communicates with a space near the external device through a third space (R3) between the external wire and the cladding part for allowing the gas in the space near the external device to be supplied to the first space (R1). a cladding part cladding the external wire ; wherein the first space (R1) communicates with a space near the external device through a third space (R3) between the external wire and the cladding part for allowing the gas in the space near the external device to be supplied to the first space (R1). <EOS>