A wiring layer forming wirings containing inner leads and outer leads are formed on a flexible substrate. Then, inner lead reinforcing electrodes to which a semiconductor chip is connected are formed on the inner leads, outer lead reinforcing electrodes are formed on the outer leads, and wiring reinforcing portions are formed between the inner leads and the outer leads on the wiring layers. The flexible substrate is mounted onto an electronic device by folding a portion to which the wiring reinforcing portions are provided between the inner leads and the outer leads.