An exhaust emission control device for an internal combustion engine, comprising: a NOx purification catalyst provided in an exhaust system of the internal combustion engine and adapted to absorb NOx in exhaust gas in an exhaust gas lean state and reduce the absorbed NOx in an exhaust gas rich state; a three-way catalyst provided upstream of the NOx purification catalyst and having oxygen storage capacity; an upstream side air-fuel ratio sensor provided upstream of the three-way catalyst and adapted to detect an exhaust gas air-fuel ratio; a downstream side air-fuel ratio sensor provided downstream of the NOx purification catalyst and adapted to detect the exhaust gas air-fuel ratio; a rich spike means for changing the air-fuel ratio of exhaust gas discharged from the internal combustion engine from lean to rich and returning the air-fuel ratio to lean after the elapse of a predetermined time to reduce and purify the NOx adsorbed by the NOx purification catalyst; a first detection means configured for detecting a NOx adsorption amount and an oxygen storage amount of the three-way catalyst and the NOx purification catalyst based on an output value of the upstream side air-fuel ratio sensor and that of the downstream side air-fuel ratio sensor during rich spike by the rich spike means; a second detection means configured for detecting the oxygen storage amount of the three-way catalyst and the NOx purification catalyst based on the output value of the upstream side air-fuel ratio sensor and that of the downstream side air-fuel ratio sensor until the exhaust gas air-fuel ratio changes to lean after the rich spike and the output of the downstream side air-fuel ratio sensor becomes lean; and a deterioration determination means configured for determining deterioration of the NOx purification catalyst based on a detected value of the first detection means and that of the second detection means wherein the deterioration determination means carries out deterioration determination for the NOx purification catalyst when bed temperature of the NOx purification catalyst is in a temperature range shifted toward a lower limit temperature side or an upper limit temperature side from temperature showing maximum NOx conversion efficiency. a NOx purification catalyst provided in an exhaust system of the internal combustion engine and adapted to absorb NOx in exhaust gas in an exhaust gas lean state and reduce the absorbed NOx in an exhaust gas rich state; a three-way catalyst provided upstream of the NOx purification catalyst and having oxygen storage capacity; an upstream side air-fuel ratio sensor provided upstream of the three-way catalyst and adapted to detect an exhaust gas air-fuel ratio; a downstream side air-fuel ratio sensor provided downstream of the NOx purification catalyst and adapted to detect the exhaust gas air-fuel ratio; a rich spike means for changing the air-fuel ratio of exhaust gas discharged from the internal combustion engine from lean to rich and returning the air-fuel ratio to lean after the elapse of a predetermined time to reduce and purify the NOx adsorbed by the NOx purification catalyst; a first detection means configured for detecting a NOx adsorption amount and an oxygen storage amount of the three-way catalyst and the NOx purification catalyst based on an output value of the upstream side air-fuel ratio sensor and that of the downstream side air-fuel ratio sensor during rich spike by the rich spike means; a second detection means configured for detecting the oxygen storage amount of the three-way catalyst and the NOx purification catalyst based on the output value of the upstream side air-fuel ratio sensor and that of the downstream side air-fuel ratio sensor until the exhaust gas air-fuel ratio changes to lean after the rich spike and the output of the downstream side air-fuel ratio sensor becomes lean; and a deterioration determination means configured for determining deterioration of the NOx purification catalyst based on a detected value of the first detection means and that of the second detection means