A power supply device includes outer case, a battery block housed in this outer case and including at least one or more secondary batteries; a circuit board connected to the battery block; and power supply connector connected to output lead that outputs an output current from the battery block. Power supply connector is attached in a floating state to fixed surface of outer case. Furthermore, the circuit board is disposed in parallel to a first direction orthogonal to fixed surface between fixed surface and the battery block. Output lead is disposed in wiring space provided in a lower side or an upper side of the circuit board, and connected to the battery block.