A power source system (5) includes a direct current power source (10), a direct current power source (20), and a power converter (50) having a plurality of switching elements (S1-S4) and reactors (L1, L2). The power converter (50) performs a direct current voltage conversion between the direct current power sources (10, 20) and a power source line (PL) in parallel by controlling the switching elements (S1-S4). Each of the switching elements (S1-S4) is disposed to be included in both a power conversion path formed between the direct current power source (10) and the power source line (PL), and a power conversion path formed between the direct current power source (20) and the power source line (PL). A phase difference (φ) between a carrier signal used for a pulse width modulation control to perform the direct current voltage conversion for the direct current power source (10), and a carrier signal used for a pulse width modulation control to perform the direct current voltage conversion for the direct current power source (20) is controlled according to the operation condition of the power converter (50).