A liquid sending device includes a plunger pump, which performs an intake operation of liquid to and a discharge operation of liquid from a pump chamber and in which pressure in the pump chamber in a case where the intake operation is performed is lower compared to a case where the discharge operation is performed, a check valve that is provided at an inlet port, has a spherical valve element and a valve seat, and passively operates according to the pressure in the pump chamber in such a direction that the valve element is seated on or detached, a pressure sensor that detects the pressure, and an attachment detector that compares the pressure with a preset threshold value and detect attachment of the valve element to the valve seat in a case where the pressure in the pump chamber is equal to or lower than the threshold value.