The application relates to fluorescent powder which has a garnet structure and can be effectively excited by ultraviolet light or blue light, a method for preparing the fluorescent powder, and a light emitting device, an image display device and an illumination device comprising the fluorescent powder. A chemical formula of the fluorescent powder is expressed as: (M1a-xM2x)ZrbM3cOd, where M1 is one or two elements selected from Sr, Ca, La, Y, Lu and Gd, Ca or Sr being necessary; M2 is one or two elements selected from Ce, Pr, Sm, Eu, Tb and Dy, Ce being necessary; M3 is at least one element selected from Ga, Si, and Ge, Ga being necessary; and 2.8≦a≦3.2, 1.9≦b≦2.1, 2.8≦c≦3.2, 11.8≦d≦12.2, and 0.002≦x≦0.6.