Liquid injection apparatus

A solenoid valve (14) opens/closes a discharge port that discharges fuel into an injection unit (15). A pressure sensor (35) installed in the fuel path, detects pressure of fuel in injection unit. An electronic control unit (ECU) (30) drives a piezoelectric element in injection unit, based on detection result, such that fuel discharged from discharge port is atomized and injected in the form of droplets.