A 360-degree projection LED bulb includes a bulb holder, a transparent bulb seat, a transparent bulb shell, an upper luminosity module, a heat dissipating seat, and a plurality of sidelight luminosity modules. The upper luminosity module includes upper LEDs supported within an upper end of the transparent bulb seat and can be driven to project light beams towards the transparent bulb shell. The heat dissipating seat is engaged on a lower end face of an upper LED substrate of the upper luminosity module and includes side walls formed as an annular polygon. Each sidelight luminosity module is mounted on an associated side wall and includes a lateral LED substrate and at least one lateral LED disposed on the lateral LED substrate. Each lateral LED can be driven to radiate horizontally and downward via the transparent bulb seat. As such, the LED bulb realizes wide-angle radiation effect and superior cooling effect.