An LED illuminating device comprising: a power source device; a controller; an LED lighting device; and an LED unit that contains LEDs (4a, 4b, 4c) emitting light at a red, blue and green emission color (R, G, B) and that is configured so as to: mix the emitted red, blue and green light of the respective LEDs (4a, 4b, 4c) at an arbitrary proportion; and set the emitted red, blue and green light in an arbitrary color mixture proportion on the basis of dimming signals (fR, fG, fB) for each of the red, blue and green light (R, G, B) from the controller, wherein the LED illuminating device is configured so that: specific coefficients (kR, kG, kB) for the red, blue and green light (R, G, B) respectively of the LED unit at which the light emitted by the LED unit becomes a predetermined default color (X, Y) in the X-Y-chromaticity diagram are set to a predetermined signal value (φR0, φG0, φB0) respectively; and the LED lighting device is configured to control an emission amount of the LEDs (4a, 4b, 4c) by using a signal values (φR, φG, φB) for the red, blue and green light (R, G, B) respectively calculated by one of the following calculation expressions: φ R = fR × kR + 1 − max fG, fB × 1 − kR or φ G = fG × kG + 1 − max fB, fR × 1 − kG; φ B = fB × kB + 1 − max fR, fG × 1 − kB φ R = fR × kR + 1 − fG × 1 − fB × 1 − kR φ G = fG × kG + 1 − fB × 1 − fR × 1 − kG; φ B = fB × kB + 1 − fR × 1 − fG × 1 − kB; wherein φR is the signal value for the red light, φG is the signal value for the green light, φB is the signal value for the blue light, fR is the dimming signal for the red light, fG is the dimming signal for the green light, fB is the dimming signal for the blue light, kR is the specific coefficient for the red light, kG is the specific coefficient for the green light and kB is the specific coefficient for the blue light. specific coefficients (kR, kG, kB) for the red, blue and green light (R, G, B) respectively of the LED unit at which the light emitted by the LED unit becomes a predetermined default color (X, Y) in the X-Y-chromaticity diagram are set to a predetermined signal value (φR0, φG0, φB0) respectively; and the LED lighting device is configured to control an emission amount of the LEDs (4a, 4b, 4c) by using a signal values (φR, φG, φB) for the red, blue and green light (R, G, B) respectively calculated by one of the following calculation expressions: φ R = fR × kR + 1 − max fG, fB × 1 − kR or φ G = fG × kG + 1 − max fB, fR × 1 − kG; φ B = fB × kB + 1 − max fR, fG × 1 − kB φ R = fR × kR + 1 − fG × 1 − fB × 1 − kR φ G = fG × kG + 1 − fB × 1 − fR × 1 − kG; φ B = fB × kB + 1 − fR × 1 − fG × 1 − kB; wherein φR is the signal value for the red light, φG is the signal value for the green light, φB is the signal value for the blue light, fR is the dimming signal for the red light, fG is the dimming signal for the green light, fB is the dimming signal for the blue light, kR is the specific coefficient for the red light, kG is the specific coefficient for the green light and kB is the specific coefficient for the blue light. φ R = fR × kR + 1 − max fG, fB × 1 − kR or φ G = fG × kG + 1 − max fB, fR × 1 − kG; φ B = fB × kB + 1 − max fR, fG × 1 − kB φ R = fR × kR + 1 − fG × 1 − fB × 1 − kR φ G = fG × kG + 1 − fB × 1 − fR × 1 − kG; φ B = fB × kB + 1 − fR × 1 − fG × 1 − kB; φR is the signal value for the red light, φG is the signal value for the green light, φB is the signal value for the blue light, fR is the dimming signal for the red light, fG is the dimming signal for the green light, fB is the dimming signal for the blue light, kR is the specific coefficient for the red light, kG is the specific coefficient for the green light and kB is the specific coefficient for the blue light.