The invention discloses an image scanning device and a control method thereof, wherein the image scanning device includes: a bearing member, configured to receive a paper bill; a light source; a lens, wherein the incidence side of the lens and the bearing member are correspondingly arranged and the lens is configured to receive reflected light or transmission light of the paper bills under the irradiation of the light source and receive emitted light of the light source; a first converter, arranged on the emergent side of the lens and configured to convert light signals from the lens into electric signals; a controller, connected with the light source and the first converter, and configured to control the light emitting time of the light source, acquire the electric signals during the light emitting process of the light source, and acquire the electric signals again after the light source stops emitting light for a preset period of time. Through the invention, the problem of low accuracy of paper bill scanning in the prior technologies is solved, and the effect of increasing the accuracy of paper bill identification is achieved.