FLUID INJECTION DEVICE AND FLUID INJECTION SYSTEM

A fluid injection device includes a valve body of a cylindrical shape and a valve member, which is movably accommodated in the valve body and which has a valve surface portion to be seated on or separated from a valve seat portion formed in an inside of the valve body. The valve member has an inside passage through which urea aqueous solution flows and a communication port, which is opened at an outer peripheral surface of the valve member and at a position of an upstream side of the valve surface portion in a flow direction of air. An annular fluid passage, through which the air flows, is formed between an inner peripheral surface of the valve body and the outer peripheral surface of the valve member. The communication port is connected to the annular fluid passage at a connecting passage portion. A cross-sectional passage area of the annular fluid passage at the connecting passage portion is smaller than a cross-sectional passage area of the annular fluid passage at an upstream-side passage portion thereof.