An image pickup apparatus comprising: image pickup means configured to photoelectrically convert an optical image of an object, the optical image having passed through an optical member, to thereby output the optical image as image data; acquisition means configured to acquire a status of the optical member; first calculation means configured to calculate a first correction value (β) for correcting image quality degradation due to characteristics of the optical member, based on characteristic information on the optical member and the status of the optical member acquired by said acquisition means; and characterised by: second calculation means configured to set a rate of change at which a second correction value (γ) is made closer to the first correction value (β) (S405, S406) and to repeatedly calculate the second correction value (γ) according to the first correction value and the rate of change by calculating the second correction value by adding a value obtained by multiplying a difference (β - α) between the first correction value and the preceding value of the second correction value by a coefficient (A,B) smaller than one and greater than zero, corresponding to the rate of change, to the preceding value (α) of the second correction value (γ), wherein when the first correction value (β) is greater than the preceding value (α) of the second correction value, the coefficient is set to be less than when the first correction value is not greater than the preceding value of the second correction value; and correction means configured to correct the image data based on the second correction value calculated by said second calculation means image pickup means configured to photoelectrically convert an optical image of an object, the optical image having passed through an optical member, to thereby output the optical image as image data; acquisition means configured to acquire a status of the optical member; first calculation means configured to calculate a first correction value (β) for correcting image quality degradation due to characteristics of the optical member, based on characteristic information on the optical member and the status of the optical member acquired by said acquisition means; and characterised by: second calculation means configured to set a rate of change at which a second correction value (γ) is made closer to the first correction value (β) (S405, S406) and to repeatedly calculate the second correction value (γ) according to the first correction value and the rate of change by calculating the second correction value by adding a value obtained by multiplying a difference (β - α) between the first correction value and the preceding value of the second correction value by a coefficient (A,B) smaller than one and greater than zero, corresponding to the rate of change, to the preceding value (α) of the second correction value (γ), wherein when the first correction value (β) is greater than the preceding value (α) of the second correction value, the coefficient is set to be less than when the first correction value is not greater than the preceding value of the second correction value; and correction means configured to correct the image data based on the second correction value calculated by said second calculation means second calculation means configured to set a rate of change at which a second correction value (γ) is made closer to the first correction value (β) (S405, S406) and to repeatedly calculate the second correction value (γ) according to the first correction value and the rate of change by calculating the second correction value by adding a value obtained by multiplying a difference (β - α) between the first correction value and the preceding value of the second correction value by a coefficient (A,B) smaller than one and greater than zero, corresponding to the rate of change, to the preceding value (α) of the second correction value (γ), wherein when the first correction value (β) is greater than the preceding value (α) of the second correction value, the coefficient is set to be less than when the first correction value is not greater than the preceding value of the second correction value; and correction means configured to correct the image data based on the second correction value calculated by said second calculation means