An image signal processing apparatus including a first conversion processing unit performing conversion processing for a left-eye image signal used to display a left-eye image so as to adjust a horizontal and/or vertical size of the left-eye image and correct a vertical bow-like distortion of the left-eye image, a second conversion processing unit performing conversion processing for a right-eye image signal used to display a right-eye image so as to adjust a horizontal and/or vertical size of the right-eye image and correct a vertical bow-like distortion of the right-eye image, and a merging unit obtaining an output image signal by merging a left-eye image signal obtained by performing the conversion processing through the first conversion processing unit and a right-eye image signal obtained by performing the conversion processing through the second conversion processing unit is provided.