A power storage unit suitable for a wearable device is provided. A novel power storage unit or power storage device is provided. The power storage unit includes a positive electrode and a negative electrode inside an external body. The positive electrode includes a positive electrode tab portion protruding from the positive electrode in one direction. The negative electrode includes a negative electrode tab portion protruding from the negative electrode in one direction. The power storage unit includes a first lead electrode electrically connected to the positive electrode tab portion and a second lead electrode electrically connected to the negative electrode tab portion. The first lead electrode includes a first fold portion. The second lead electrode includes a second fold portion.