Abstract: In a memory card having circuit elements such as a semiconductor device and transmitting/receiving device mounted on a synthetic resin substrate shaped like a flat plate, the circuit elements are disposed and sealed in the synthetic resin substrate, and both surfaces of the substrate are covered with synthetic resin sheet members. This achieves a memory card, which is resistant to bending and also survives harsh operating environment. Also provided are a memory card, which can be easily developed into a multi-function card such as an ID card at low cost, and its manufacturing method.