A hot water system for a bidet having a housing is provided. The hot water system includes: a water inlet pipe connected to a faucet; a flow path guide tank located at a lower portion in the housing so that water introduced into the water inlet pipe flows; a sheath heater provided in the housing and configured to heat water discharged from the flow path guide tank; and a water outlet pipe configured to supply water heated by the sheath heater to the outside. The flow path guide tank has a flow path guide hole formed through in an upward direction so that water introduced into the water inlet pipe flows into an upper portion inside the housing and exchanges heat with the sheath heater.