Patent ID: 8888094

Claim:
A conveying device comprising: a first conveyor unit that conveys a printing medium; a second conveyor unit that is disposed on a conveying path on a downstream side of the first conveyor unit and conveys the printing medium; a medium detecting unit that is disposed between the first and second conveyor units, including a light emitting part emitting light to the conveying path and a light receiving part disposed so as to face the light emitting part with the conveying path interposed therebetween and receives the light emitted from the light emitting part, and acquires an amount of light, which passes through the printing medium conveyed along the conveying path and is received by the light receiving part, as an amount of received light; a storage unit that stores a double-feed criterion amount of received light created on a basis of the amount of received light acquired by the medium detecting unit; and a controller that makes a conveying speed of the printing medium conveyed by the first conveyor unit higher than a conveying speed of the printing medium conveyed by the second conveyor unit, and makes the printing medium to be conveyed while forming a sag on the printing medium between the first and second conveyor units, wherein the controller makes the medium detecting unit acquire the amount of received light according to a conveying distance of the printing medium conveyed along the conveying path, and determines that the double-feed of the printing media has occurred when the amount of received light is smaller than the double-feed criterion amount of received light at substantially the same conveying distance of the printing medium and a difference therebetween is equal to or larger than a predetermined threshold.