To provide an image signal processor and processing method in which IP conversion can be carried out accurately using a small memory capacity without causing any deterioration of image quality.

Movement at the time of IP conversion is detected using the data of current field and the data of two field delay (one frame delay) by determining a function representative of a movement due to the absolute value of difference between two data. Maximum value of movements V1 and V2 determined from the data of pixels C, D, E and F of lines before and after a pixel R for detecting the movement is determined as the movement of the pixel R. Depending on that movement, a DSP 11 operates the interpolation data of current field using data of in-field interpolation determined from the data of pixels C and D of the lines before and after the pixel R and data of pixel G of one field delay at the same position as the pixel for detecting the movement.