A water pump for a vehicle includes a shaft for receiving rotational power from the engine; an impeller mounted on the shaft to pump the coolant discharged from the engine; and a housing where the shaft and the impeller are embedded, disposed in a direction opposite to the direction to which the shaft is connected with respect to the impeller to have a coolant inflow passage, into which the coolant discharged from the engine flows, formed therein, disposed along the edge of the impeller to have a coolant discharge passage for discharging the coolant pumped by the impeller to the heat exchanging means formed therein, and disposed in the direction to which the shaft is connected to have a bypass passage for discharging the coolant to the engine formed therein, and the housing has a connecting passage for connecting the coolant inflow passage and the bypass passage formed therein.