There is provided a phosphor powder which includes a wavelength converting material and a silica-based inorganic substance surrounding the wavelength converting material and represented by the following Formula 1, wherein a content of a hydrosilyl group (Si—H) is greater than or equal to 10 ppm by weight, based on the total weight of the silica-based inorganic substance: wherein X represents oxygen (O) or an amine group (NH), Y represents hydrogen (H), a hydroxyl group (OH), an amino group (NH2), or an alkyl group containing heteroelements, and the heteroelements include at least one selected from the group consisting of phosphorus (P), nitrogen (N), sulfur (S), oxygen (O), and a halogen element.