With an increase in the degree of integration or the processing speed of semiconductor devices and a reduction in power consumption, the development of small and high-performance information communication apparatuses, such as mobile phone, electronic dictionaries, and digital video cameras has been accelerated. Various kinds of memory cards including memory devices for storing information can be inserted into or removed from the mobile apparatuses in a card edge type (for example, see Patent Document 1). USB-type (Universal Serial Bus) concave connectors that are mainly used in personal computers as well as card-insertion-type concave connectors have been utilized in order to control peripheral devices each other, such as a printer, a mouse, and a measuring device. In recent years, internationally standardized concave connectors for connection to parts mounting LEDs that have been developed have drawn attention. In a flexible rigid plate in which a flexible rigid substrate is used in a common inner layer in order to connect multi-layered printed circuit boards each other, a structure has been proposed in which a concave connection portion is provided in the multi-layered substrate, not the common inner layer (for example, see Patent Document 2).