A vehicle-mountable exhaust gas analyzer that is mountable in a vehicle and that is configured to measure concentration of a component as an object to be measured such as THC, CO and CO 2 contained in exhaust gas discharged from a vehicle, comprising; a drain separator connected to an exhaust duct of the vehicle through an unheated piping which is configured to cool the exhaust gas discharged from the vehicle to a normal temperature so that H 2 O contained in the exhaust gas condensates and attaches to inside the unheated piping as liquid H 2 O, and the liquid H 2 O is discharged out of the unheated piping through the drain separator, a measuring instrument group (4, 5, 6) that is configured to measure concentration of H 2 O in the exhaust gas and concentration of the component as the object to be measured in a semi-dry state wherein liquid H 2 O is removed by the drain separator, a correction part that is configured to calculate a true measurement value concerning the concentration of CO, CO 2 and H 2 O in the semi-dry state by conducting intermediate correction on each actual measurement value of the concentration of CO, CO 2, and H 2 O based on the actual measurement value of the concentration of THC, and further conducting correction on the intermediate correction value of the concentration of CO and CO 2 based on the intermediate correction value of the concentration of CO, CO 2 and H 2 O, a dry concentration calculating part that is configured to calculate concentration of the component as the object to be measured in the exhaust gas in a dry state wherein H 2 O is completely removed based on the true measurement value obtained by the correction part, and an actual concentration calculating part that is configured to calculate concentration of the component as the object to be measured contained in the exhaust gas at a time when the exhaust gas is discharged from the vehicle based on the concentration of the component in the dry state and a predetermined conversion equation. a drain separator connected to an exhaust duct of the vehicle through an unheated piping which is configured to cool the exhaust gas discharged from the vehicle to a normal temperature so that H 2 O contained in the exhaust gas condensates and attaches to inside the unheated piping as liquid H 2 O, and the liquid H 2 O is discharged out of the unheated piping through the drain separator, a measuring instrument group (4, 5, 6) that is configured to measure concentration of H 2 O in the exhaust gas and concentration of the component as the object to be measured in a semi-dry state wherein liquid H 2 O is removed by the drain separator, a correction part that is configured to calculate a true measurement value concerning the concentration of CO, CO 2 and H 2 O in the semi-dry state by conducting intermediate correction on each actual measurement value of the concentration of CO, CO 2, and H 2 O based on the actual measurement value of the concentration of THC, and further conducting correction on the intermediate correction value of the concentration of CO and CO 2 based on the intermediate correction value of the concentration of CO, CO 2 and H 2 O, calculate a true measurement value concerning the concentration of CO, CO 2 and H 2 O in the semi-dry state by conducting intermediate correction on each actual measurement value of the concentration of CO, CO 2, and H 2 O based on the actual measurement value of the concentration of THC, and further conducting correction on the intermediate correction value of the concentration of CO and CO 2 based on the intermediate correction value of the concentration of CO, CO 2 and H 2 O, a dry concentration calculating part that is configured to calculate concentration of the component as the object to be measured in the exhaust gas in a dry state wherein H 2 O is completely removed based on the true measurement value obtained by the correction part, and an actual concentration calculating part that is configured to calculate concentration of the component as the object to be measured contained in the exhaust gas at a time when the exhaust gas is discharged from the vehicle based on the concentration of the component in the dry state and a predetermined conversion equation.