A printer includes a lid part, a body part, a control part provided in the body part, a mark detecting part provided on the lid part and configured to output a mark detection signal in response to detecting a mark added to paper, a transmission part configured to transmit the mark detection signal from the mark detecting part to the control part and having a slack part configured to extend and contract, and a housing part configured to house the slack part of the transmission part and to extend and contract in directions in which the slack part is configured to extend and contract. The slack part is housed in the housing part, and a length of the slack part is greater than or equal to a length of the housing part.