Three-color mixing led illuminating device

An LED illuminating device comprising:

• a housing comprising a base plate;
• a prism sheet mounted in the housing and comprising a plurality of V-shaped micro-grooves formed along two directions intersecting with each other;
• a circuit board fixed on the base plate, wherein a plurality of LED units are arranged on the circuit board in groups, each group comprises four LED units, each of the four LED units emitting light of a color and the four LED units emitting light of three colors in total, two adjacent groups share a LED unit;
• four virtual mixed light sources are formed by reflection of the prism sheet to the circuit board when the light emitted by a particular LED unit in a particular group mixes with light emitted by others in the particular group on the circuit board, each of the virtual mixed light sources forms a desired color different from the colors of the light emitted from the LED units.