An exhaust gas purification apparatus for an internal combustion engine, comprising: an oxidation catalyst suitable to be provided in an exhaust gas passage of the internal combustion engine and having an oxidation capability, the oxidation catalyst exhibiting an action of adsorbing NOx in an exhaust gas flowing therein and an action of reducing NOx in the exhaust gas by using a hydrocarbon in the exhaust gas flowing therein as a reducing agent, when a temperature of the oxidation catalyst is in a predetermined temperature range; a NOx sensor which is provided at a downstream side of the oxidation catalyst for detecting a NOx concentration in the exhaust gas; a fault determination unit for executing a fault determination of the NOx sensor on the basis of a comparison between a detected value of the NOx concentration detected by the NOx sensor and an estimated value of the NOx concentration in the exhaust gas at the position of the NOx sensor, and an estimation unit; characterized in that when the temperature of the oxidation catalyst is in the predetermined temperature range, - the estimation unit estimates an adsorption rate, which is an amount of NOx adsorbed to the oxidation catalyst per unit time, and a desorption rate, which is an amount of NOx desorbed from the oxidation catalyst per unit time, on the basis of a hydrocarbon flow rate in the exhaust gas flowing into the oxidation catalyst and the temperature of the oxidation catalyst, and - the fault determination unit -- halts the fault determination of the NOx sensor when a net desorption amount of the NOx obtained from the adsorption rate and the desorption rate is equal to or greater than a predetermined amount, or -- uses a corrected estimated value, which is the estimated value corrected on the basis of the adsorption rate and the desorption rate, instead of the estimated value to execute the fault determination of the NOx sensor. an oxidation catalyst suitable to be provided in an exhaust gas passage of the internal combustion engine and having an oxidation capability, the oxidation catalyst exhibiting an action of adsorbing NOx in an exhaust gas flowing therein and an action of reducing NOx in the exhaust gas by using a hydrocarbon in the exhaust gas flowing therein as a reducing agent, when a temperature of the oxidation catalyst is in a predetermined temperature range; a NOx sensor which is provided at a downstream side of the oxidation catalyst for detecting a NOx concentration in the exhaust gas; a fault determination unit for executing a fault determination of the NOx sensor on the basis of a comparison between a detected value of the NOx concentration detected by the NOx sensor and an estimated value of the NOx concentration in the exhaust gas at the position of the NOx sensor, and an estimation unit; characterized in that when the temperature of the oxidation catalyst is in the predetermined temperature range, - the estimation unit estimates an adsorption rate, which is an amount of NOx adsorbed to the oxidation catalyst per unit time, and a desorption rate, which is an amount of NOx desorbed from the oxidation catalyst per unit time, on the basis of a hydrocarbon flow rate in the exhaust gas flowing into the oxidation catalyst and the temperature of the oxidation catalyst, and - the fault determination unit -- halts the fault determination of the NOx sensor when a net desorption amount of the NOx obtained from the adsorption rate and the desorption rate is equal to or greater than a predetermined amount, or -- uses a corrected estimated value, which is the estimated value corrected on the basis of the adsorption rate and the desorption rate, instead of the estimated value to execute the fault determination of the NOx sensor. - the estimation unit estimates an adsorption rate, which is an amount of NOx adsorbed to the oxidation catalyst per unit time, and a desorption rate, which is an amount of NOx desorbed from the oxidation catalyst per unit time, on the basis of a hydrocarbon flow rate in the exhaust gas flowing into the oxidation catalyst and the temperature of the oxidation catalyst, and - the fault determination unit -- halts the fault determination of the NOx sensor when a net desorption amount of the NOx obtained from the adsorption rate and the desorption rate is equal to or greater than a predetermined amount, or -- uses a corrected estimated value, which is the estimated value corrected on the basis of the adsorption rate and the desorption rate, instead of the estimated value to execute the fault determination of the NOx sensor. -- halts the fault determination of the NOx sensor when a net desorption amount of the NOx obtained from the adsorption rate and the desorption rate is equal to or greater than a predetermined amount, or -- uses a corrected estimated value, which is the estimated value corrected on the basis of the adsorption rate and the desorption rate, instead of the estimated value to execute the fault determination of the NOx sensor.