1. An image processing apparatus comprising: an input unit configured to input first video data captured based on a first capturing parameter and second video data captured based on a second capturing parameter; an evaluation unit configured to obtain a first temporal noise evaluation value for the first video data based on the first video data and a temporal visual property corresponding to the first video data, a first spatial noise evaluation value for the first video data based on the first video data and a spatial visual property corresponding to the first video data, a second temporal noise evaluation value for the second video data based on the second video data and a temporal visual property corresponding to the second video data, and a second spatial noise evaluation value for the second video data based on the second video data and a spatial visual property corresponding to the second video data; an added noise determination unit configured to determine noise data to be added to at least one of the first and second video data based on the first and second temporal noise evaluation values corresponding to the first and second video data and the first and second spatial noise evaluation values corresponding to the first and second video data, so that a difference between a temporal noise evaluation value corresponding to the first video data and a temporal noise evaluation value corresponding to the second video data after addition of the noise data is smaller than a difference between the first and second temporal noise evaluation values and so that a difference between a spatial noise evaluation value corresponding to the first video data and a spatial noise evaluation value corresponding to the second video data after addition of the noise data is smaller than a difference between the first and second spatial noise evaluation values; and a noise adding unit configured to add the noise data to at least one of first and second video data.