A gas detection and purification device can be placed in an in-car space and includes a housing, a purification module, a gas-guiding unit, and a gas detection module. The housing has a gas inlet and a gas outlet. A gas channel is between the gas inlet and the gas outlet. The purification module is disposed in the gas channel to filter the gas guided into the gas channel. The gas-guiding unit is disposed in the gas channel and at one side of the purification module. The gas-guiding unit guides the gas into the device from the gas inlet, guides the gas to pass through the purification module for performing filtering and purifying, and discharges the gas out from the gas outlet. The gas detection module is disposed in the gas channel to detect the gas guided into the housing to obtain gas detection data.