A developer, comprising at least: toner particles each containing at least a binder resin; and a composite inorganic powder, wherein: the composite inorganic powder has a number average particle diameter of 30 nm or more to less than 1,000 nm, wherein the number average particle diameter is the average of the particle diameters of 100 particles measured in a picture photographed at a magnification of 50,000 with an electron microscope the composite inorganic powder has a peak at a Bragg angle (2θ ± 0.20 deg) of each of 32.20 deg, 25.80 deg, and 27.50 deg in a CuKα characteristic X-ray diffraction pattern, as measured in accordance with the description; wherein the peak at 32.20 deg originates from the (1, 1, 0) surface of a strontium titanate crystal, the peak at 25.80 deg originates from strontium carbonate, and the peak at 27.50 deg originates from titanium oxide; and a half width of the X-ray diffraction peak, as determined in accordance with the description, at a Bragg angle (2θ ± 0.20 deg) of 32.20 deg is 0.20 to 0.30 deg, wherein an intensity level (Ia) of the peak at a Bragg angle (2θ ± 0.20 deg) of 32.20 deg in the CuKα characteristic X-ray diffraction pattern of the composite inorganic powder, an intensity level (Ib) of the peak at a Bragg angle of 25.80 deg in the pattern, and an intensity level (Ic) of the peak at a Bragg angle of 27.50 deg in the pattern satisfy the following formulae: 0.010 < Ib / Ia < 0.150 0.010 < Ic / Ia < 0.150. toner particles each containing at least a binder resin; and a composite inorganic powder, wherein: the composite inorganic powder has a number average particle diameter of 30 nm or more to less than 1,000 nm, wherein the number average particle diameter is the average of the particle diameters of 100 particles measured in a picture photographed at a magnification of 50,000 with an electron microscope the composite inorganic powder has a peak at a Bragg angle (2θ ± 0.20 deg) of each of 32.20 deg, 25.80 deg, and 27.50 deg in a CuKα characteristic X-ray diffraction pattern, as measured in accordance with the description; wherein the peak at 32.20 deg originates from the (1, 1, 0) surface of a strontium titanate crystal, the peak at 25.80 deg originates from strontium carbonate, and the peak at 27.50 deg originates from titanium oxide; and a half width of the X-ray diffraction peak, as determined in accordance with the description, at a Bragg angle (2θ ± 0.20 deg) of 32.20 deg is 0.20 to 0.30 deg, wherein an intensity level (Ia) of the peak at a Bragg angle (2θ ± 0.20 deg) of 32.20 deg in the CuKα characteristic X-ray diffraction pattern of the composite inorganic powder, an intensity level (Ib) of the peak at a Bragg angle of 25.80 deg in the pattern, and an intensity level (Ic) of the peak at a Bragg angle of 27.50 deg in the pattern satisfy the following formulae: 0.010 < Ib / Ia < 0.150 0.010 < Ic / Ia < 0.150. the composite inorganic powder has a number average particle diameter of 30 nm or more to less than 1,000 nm, wherein the number average particle diameter is the average of the particle diameters of 100 particles measured in a picture photographed at a magnification of 50,000 with an electron microscope the composite inorganic powder has a peak at a Bragg angle (2θ ± 0.20 deg) of each of 32.20 deg, 25.80 deg, and 27.50 deg in a CuKα characteristic X-ray diffraction pattern, as measured in accordance with the description; wherein the peak at 32.20 deg originates from the (1, 1, 0) surface of a strontium titanate crystal, the peak at 25.80 deg originates from strontium carbonate, and the peak at 27.50 deg originates from titanium oxide; and a half width of the X-ray diffraction peak, as determined in accordance with the description, at a Bragg angle (2θ ± 0.20 deg) of 32.20 deg is 0.20 to 0.30 deg, wherein an intensity level (Ia) of the peak at a Bragg angle (2θ ± 0.20 deg) of 32.20 deg in the CuKα characteristic X-ray diffraction pattern of the composite inorganic powder, an intensity level (Ib) of the peak at a Bragg angle of 25.80 deg in the pattern, and an intensity level (Ic) of the peak at a Bragg angle of 27.50 deg in the pattern satisfy the following formulae: 0.010 < Ib / Ia < 0.150 0.010 < Ic / Ia < 0.150.