An illumination lighting device is provided with: a power
converter circuit having a configuration in which an input terminal to which a power supply can be connected and an output terminal to which a
load circuit including at least a lamp can be connected are galvanically insulated, and having a power regulating function required by the lamp; output detection means which is provided at the output terminal of the power
converter circuit and has first current detection means and second current detection means; and a
control circuit for regulating the output of the power
converter circuit based on a result of detection performed by the output detection means, wherein one end of the output of the power converter circuit is connected to one end of the
load circuit via the first current detection means, one end of an input of the power converter circuit is connected to the one end of the
load circuit via the second current detection means, the output detection means has the result of the detection which is a synthesized
signal of detection outputs of the first current detection means and the second current detection means, a current pathway, through which a ground-fault current flows from the one end of the input of the power converter circuit to the one end of the output of the power converter circuit via the first current detection means and the second current detection means, is formed when a ground fault occurs at a load terminal of the load circuit, and a detection
signal of the first current detection means and a detection
signal of the second current detection means that result from the ground-fault current are of additive polarities.