An image pickup system comprising: a light source configured to emit light for illuminating an object; an image sensor configured to receive light from the object and perform an image pickup operation using a rolling-shutter method in which exposure and readout are performed in a predetermined time cycle; a timing generator configured to generate a driving signal to control the image sensor such that exposure and readout are performed in the image sensor in the predetermined time cycle; characterized by: an image adding section configured to add image pickup signals for N frames from an image pickup signal including a predetermined frame, which is read out from the image sensor, to an image pickup signal in an Nth frame (N is an integer equal to or greater than 2) with the predetermined frame being set as a first frame, and output the added image pickup signals; a trigger signal output section configured to output a trigger signal which represents either a first timing at which readout of a first line in the predetermined frame is started in the image sensor or a second timing at which readout of a last line in a frame immediately before the predetermined frame has been completed in the image sensor; a light source control section configured to perform control to start light emission by the light source at a timing after a predetermined delay period has elapsed after an input from the trigger signal output section and terminate light emission by the light source in a period after completion of readout of a first line in an N-1th frame, with the predetermined frame as a reference, until before a start of a first line in the Nth frame. a light source configured to emit light for illuminating an object; an image sensor configured to receive light from the object and perform an image pickup operation using a rolling-shutter method in which exposure and readout are performed in a predetermined time cycle; a timing generator configured to generate a driving signal to control the image sensor such that exposure and readout are performed in the image sensor in the predetermined time cycle; characterized by: an image adding section configured to add image pickup signals for N frames from an image pickup signal including a predetermined frame, which is read out from the image sensor, to an image pickup signal in an Nth frame (N is an integer equal to or greater than 2) with the predetermined frame being set as a first frame, and output the added image pickup signals; a trigger signal output section configured to output a trigger signal which represents either a first timing at which readout of a first line in the predetermined frame is started in the image sensor or a second timing at which readout of a last line in a frame immediately before the predetermined frame has been completed in the image sensor; a light source control section configured to perform control to start light emission by the light source at a timing after a predetermined delay period has elapsed after an input from the trigger signal output section and terminate light emission by the light source in a period after completion of readout of a first line in an N-1th frame, with the predetermined frame as a reference, until before a start of a first line in the Nth frame.