Provided is an image pick-up semiconductor device capable of testing operating characteristics of an analog-digital converter while the image pick-up semiconductor device operates. The device includes an active pixel sensor array having a plurality of pixels converting optical signals input from an external source into electrical signals, a columnar analog-digital converter converting signals output from the active pixel sensor array into first digital data, and a test analog-digital converter receiving two external signals and converting a voltage difference between the two external signals into second digital data.