The present invention relates to a piston cooling device for cooling a piston. The piston cooling device according to an exemplary embodiment of the present invention includes: a cooling channel that is formed in a piston such that cooling fluid flows, and communicates with an intake port through which cooling fluid flows inside from the outside at a point and with an exhaust port through which the cooling fluid is discharged outside at another point; and a flow guide part that is formed in the cooling channel and guides the cooling fluid, which flows in the cooling channel through the intake port when the piston moves up or down, to flow to the exhaust port through the cooling channel.