A printer comprising: storage means configured to detachably store a print-receiving medium comprising a plurality of identifiers for positioning; feeding means configured to feed said print-receiving medium stored in said storage means; printing means configured to perform desired printing on said print-receiving medium fed in a forward direction along a transport direction by said feeding means; detecting means configured to detect said identifier of said print-receiving medium, disposed on a feeding path of said print-receiving medium by said feeding means; instruction input means for inputting an operation instruction for starting print processing; and first control means for controlling said feeding means so as to start feeding of said print-receiving medium in said forward direction, in accordance with said operation instruction for starting print processing via said instruction input means, characterized by detection determining means for determining whether or not said detecting means detects said identifier after feeding of said print-receiving medium in said forward direction was started by said first control means; second control means for controlling said feeding means so as to feed said print-receiving medium in a reverse direction that is reverse to said forward direction, and to position a position of said print-receiving medium along said transport direction in a predetermined first initial position in a case that said detection determining means determined that said detecting means detects said identifier; reverse determining means configured to determine whether or not a predetermined reversability condition related to a feeding of said print-receiving medium in said reverse direction based on control of said second control means has been satisfied; and third control means configured to control said feeding means so as to further feed said print receiving medium in said forward direction, and to position the position of said print-receiving medium along said transport direction in a predetermined second initial position when said reverse determining means has determined that said reversability condition has not been satisfied and said detection determining means determined that said detecting means detected said identifier, wherein: said second control means controls said feeding means so as to feed said print-receiving medium in said reverse direction and to perform said positioning when said reverse determining means determined that said reversability condition has been satisfied and said detection determining means determined that said detecting means detected said identifier. storage means configured to detachably store a print-receiving medium comprising a plurality of identifiers for positioning; feeding means configured to feed said print-receiving medium stored in said storage means; printing means configured to perform desired printing on said print-receiving medium fed in a forward direction along a transport direction by said feeding means; detecting means configured to detect said identifier of said print-receiving medium, disposed on a feeding path of said print-receiving medium by said feeding means; instruction input means for inputting an operation instruction for starting print processing; and first control means for controlling said feeding means so as to start feeding of said print-receiving medium in said forward direction, in accordance with said operation instruction for starting print processing via said instruction input means, characterized by detection determining means for determining whether or not said detecting means detects said identifier after feeding of said print-receiving medium in said forward direction was started by said first control means; second control means for controlling said feeding means so as to feed said print-receiving medium in a reverse direction that is reverse to said forward direction, and to position a position of said print-receiving medium along said transport direction in a predetermined first initial position in a case that said detection determining means determined that said detecting means detects said identifier; reverse determining means configured to determine whether or not a predetermined reversability condition related to a feeding of said print-receiving medium in said reverse direction based on control of said second control means has been satisfied; and third control means configured to control said feeding means so as to further feed said print receiving medium in said forward direction, and to position the position of said print-receiving medium along said transport direction in a predetermined second initial position when said reverse determining means has determined that said reversability condition has not been satisfied and said detection determining means determined that said detecting means detected said identifier, wherein: said second control means controls said feeding means so as to feed said print-receiving medium in said reverse direction and to perform said positioning when said reverse determining means determined that said reversability condition has been satisfied and said detection determining means determined that said detecting means detected said identifier.