An image processing apparatus comprising: first screen processing means configured to perform screen processing on input image data using a first screen information; evaluation means configured to acquire an evaluation value of a processing result of the first screen processing means based on a difference between a low-frequency component of the processing result of the first screen processing means and a low-frequency component of the input image data; setting means configured to set a set screen information acquired by performing calculation using the first screen information and a second screen information that is different from the first screen information, according to an evaluation value of a processing result of the first screen processing means, wherein at least a part of threshold values of the set screen information is generated using first threshold values (Ba_Th_c, Ba_Th_m, Ba_Th_y, Ba_Th_bk) in the first screen information and second threshold values (L_Th_c, L_Th_m, L_Th_y, L_Th_bk) in the second screen information, said part of the threshold values of the set screen information being generated by weighted combinations of the first threshold values and the second threshold values; and second screen processing means configured to perform screen processing on the input image data using the set screen information; wherein the second screen information is a line screen information, and a screen vector (L_c_V) acquired from the line screen information is indicated by linear combination of two screen vectors (Ba_V, Ba_V) configuring the first screen information, and each coefficient used in said combination is an integer or a fraction. first screen processing means configured to perform screen processing on input image data using a first screen information; evaluation means configured to acquire an evaluation value of a processing result of the first screen processing means based on a difference between a low-frequency component of the processing result of the first screen processing means and a low-frequency component of the input image data; setting means configured to set a set screen information acquired by performing calculation using the first screen information and a second screen information that is different from the first screen information, according to an evaluation value of a processing result of the first screen processing means, wherein at least a part of threshold values of the set screen information is generated using first threshold values (Ba_Th_c, Ba_Th_m, Ba_Th_y, Ba_Th_bk) in the first screen information and second threshold values (L_Th_c, L_Th_m, L_Th_y, L_Th_bk) in the second screen information, said part of the threshold values of the set screen information being generated by weighted combinations of the first threshold values and the second threshold values; and second screen processing means configured to perform screen processing on the input image data using the set screen information; wherein the second screen information is a line screen information, and a screen vector (L_c_V) acquired from the line screen information is indicated by linear combination of two screen vectors (Ba_V, Ba_V) configuring the first screen information, and each coefficient used in said combination is an integer or a fraction.