A prism sheet includes a main body. The main body includes an incident surface, an emitting surface opposite to the incident surface, and a plurality of micro-protrusions formed on the incident surface. Each micro-protrusion includes two side surfaces and an arced ridge of intersection of the two side surfaces. Each side surface is a conical surface of an imaginary cone. The imaginary cone has a conical base whose circumference is defined by the arced ridge. The conical bases defined by the arced ridges of the micro-protrusions are parallel to each other. The present prism sheet and the backlight module using the same can efficiently decrease interference.