Abstract: A polarizer includes a light-transmissible substrate, a plurality of metal wires, and a protective layer. The light-transmissible substrate has a mounting surface. The metal wires are parallelly arranged on the mounting surface of the light-transmissible substrate. Each of the metal wires extends in a direction parallel to the mounting surface, and has an upper surface and a peripheral surface. The protective layer has a first portion and a plurality of second portions. The first portion covers the upper surface of each of the metal wires and is formed into a continuous structure. Each of the second portions covers the peripheral surface of a respective one of the metal wires. Two adjacent ones of the second portions are spaced apart from each other. A light emitting device including the polarizer and a light emitting apparatus including the light emitting device are also disclosed.