A physical-quantity detection device, comprising: a circuit board including at least one detection unit (421A,421B,422,602) configured to detect a physical quantity of a gas being measured that passes through a main channel, and a circuit unit configured to perform a computation on the physical quantity detected by the detection unit; and a housing configured to accommodate the circuit board, wherein the housing is formed of a molded resin, and the circuit board is integrally molded together with the housing, wherein the housing is formed by a material made of a thermoplastic resin, and a board body of the circuit board is formed by a material made of a glass epoxy resin, wherein at least either of a through hole (404,405,406) or a notch (407,408) is disposed at a portion to be inserted into the housing of the circuit board, wherein the housing passes through the through hole or the notch, and wherein a molded resin is bonded on a front side and a back side of the circuit board, wherein the housing includes: a circuit room (Rc) in which the circuit unit is disposed; a first bypass passage in which a first detection unit is disposed, and the gas being measured flows; and a dividing wall configured to divide the circuit room and the first bypass passage, wherein the through hole or the notch is disposed at a position covered by the dividing wall or on a side of the circuit board, and wherein the housing is divided into a front surface side and a back surface side by the circuit board, the circuit room is formed on a front surface side of the housing, a sensor room (Rs) accommodating a second detection unit is formed on a back surface side of the housing, and a second bypass passage in which the gas being measured flows is disposed to communicate with the sensor room. a circuit board including at least one detection unit (421A,421B,422,602) configured to detect a physical quantity of a gas being measured that passes through a main channel, and a circuit unit configured to perform a computation on the physical quantity detected by the detection unit; and a housing configured to accommodate the circuit board, wherein the housing is formed of a molded resin, and the circuit board is integrally molded together with the housing, wherein the housing is formed by a material made of a thermoplastic resin, and a board body of the circuit board is formed by a material made of a glass epoxy resin, wherein at least either of a through hole (404,405,406) or a notch (407,408) is disposed at a portion to be inserted into the housing of the circuit board, wherein the housing passes through the through hole or the notch, and wherein a molded resin is bonded on a front side and a back side of the circuit board, wherein the housing includes: a circuit room (Rc) in which the circuit unit is disposed; a first bypass passage in which a first detection unit is disposed, and the gas being measured flows; and a dividing wall configured to divide the circuit room and the first bypass passage, wherein the through hole or the notch is disposed at a position covered by the dividing wall or on a side of the circuit board, and wherein the housing is divided into a front surface side and a back surface side by the circuit board, the circuit room is formed on a front surface side of the housing, a sensor room (Rs) accommodating a second detection unit is formed on a back surface side of the housing, and a second bypass passage in which the gas being measured flows is disposed to communicate with the sensor room.