An expansion/contraction measuring apparatus includes a transport section which transports a flexible substrate along a surface of the substrate; a detecting section detecting first and second marks which are formed on the substrate while being separated from each other by a predetermined spacing distance in a transport direction of the substrate and which are moved, in accordance with the transport of the substrate, to first and second detection areas disposed on a transport route for the substrate respectively; a substrate length setting section which sets a length of the substrate along the transport route between the first and second detection areas to a reference length; and a deriving section which derives information about expansion/contraction of the substrate in relation to the transport direction based on a detection result of the first and second marks. Accordingly, the expansion/contraction state of an expandable/contractible substrate is measured highly accurately.