1. An apparatus for generating a depth signal for each of time-series images, the time series images including a first image and a second image, the apparatus comprising: a calculating unit configured to calculate a statistic value for pixel values of pixels for each of predefined areas in the first image, and calculate, for each of predetermined base depth models, a first evaluation value based on the calculated statistic value, each of the predetermined base depth models having a depth structure pattern; a correcting unit configured to correct, based on a second evaluation value previously derived for the second image and a first degree of similarity indicating a similarity between the predetermined base depth models, the first evaluation value to derive second evaluation values for the predetermined base depth models; a selecting unit configured to select a base depth model having a highest second evaluation value, from the predetermined base depth models; and a generating unit configured to generate a depth signal based on the selected base depth model.