A control apparatus for an internal combustion engine, the control apparatus comprising: an electronic control unit configured to: estimate a characteristic value indicating divergence from a reference value of an intake air volume, based on an actually detected indicator value of the intake air volume and an opening degree of a throttle valve; store the characteristic value as a learnt value in association with the opening degree of the throttle valve at a time when the indicator value is detected; calculate, in association with each opening degree of the throttle valve, the characteristic value for an opening degree of the throttle valve for which learning has not been completed, by linear interpolation using the learnt values; learn the characteristics of the throttle valve and reflect the characteristics in control of the intake air volume, based on the characteristic values associated with the opening degrees; update the learnt value for an opening degree of the throttle valve at which an engine rotation speed is equal to or greater than an idling rotation speed, by associating the characteristic value with the opening degree of the throttle valve at the time when the indicator value is detected and storing the characteristic value and the opening degree of the throttle valve at the time when the indicator value is detected, during an initial engine operation after initialization of the learnt values; characterized in that the electronic control unit is further configured to update the learnt value for an opening degree of the throttle valve at which the engine rotation speed is lower than the idling rotation speed, by storing a value equal to the learnt value for the smallest opening degree for which learning has already been completed, from among the opening degrees at which the engine rotation speed is equal to or greater than the idling rotation speed, and the updating of the learnt values is not carried out by associating the characteristic value with the opening degree of the throttle valve at the time when the indicator value is detected and storing the characteristic value and the opening degree of the throttle valve at the time when the indicator value is detected. estimate a characteristic value indicating divergence from a reference value of an intake air volume, based on an actually detected indicator value of the intake air volume and an opening degree of a throttle valve; store the characteristic value as a learnt value in association with the opening degree of the throttle valve at a time when the indicator value is detected; calculate, in association with each opening degree of the throttle valve, the characteristic value for an opening degree of the throttle valve for which learning has not been completed, by linear interpolation using the learnt values; learn the characteristics of the throttle valve and reflect the characteristics in control of the intake air volume, based on the characteristic values associated with the opening degrees; update the learnt value for an opening degree of the throttle valve at which an engine rotation speed is equal to or greater than an idling rotation speed, by associating the characteristic value with the opening degree of the throttle valve at the time when the indicator value is detected and storing the characteristic value and the opening degree of the throttle valve at the time when the indicator value is detected, during an initial engine operation after initialization of the learnt values; characterized in that the electronic control unit is further configured to update the learnt value for an opening degree of the throttle valve at which the engine rotation speed is lower than the idling rotation speed, by storing a value equal to the learnt value for the smallest opening degree for which learning has already been completed, from among the opening degrees at which the engine rotation speed is equal to or greater than the idling rotation speed, and the updating of the learnt values is not carried out by associating the characteristic value with the opening degree of the throttle valve at the time when the indicator value is detected and storing the characteristic value and the opening degree of the throttle valve at the time when the indicator value is detected.