A lighting device comprising: a power conversion part including a switching element and receiving DC power as an input in order to adjust power supplied to a light source load by an operation to turn on/off the switching element; a control part (6, 7) receiving a power setting value (Ws) adapted to determine size of power supplied to the light source load and to control the power conversion part; a current detection part adapted to detect a current flowing in the switching element and to obtain a corresponding current detection value; a power estimation part adapted to estimate the input power (Win) of the lighting device; characterized by a presentation part adapted to present the estimated input power (Win) of the lighting device to a user or to notify the estimated input power (Win) of the lighting device to an external device, the power estimation part estimates the input power (Win) by using the power setting value (Ws) and the current detection value, thereby providing correction of the input power (Win) estimation for fluctuations of the current detection value caused by a change in the ambient temperature of the light source load by means of the following calculation: - calculating a ratio by dividing the power setting value (Ws) by a stored maximum power value (Wmax), which corresponds to the power setting value obtained in response to maximum power supplied to the light source load, and multiplying said ratio with a preset coefficient (α) to obtain a frist value, - subtracting a power adjustment value (Vfb) from said first value obtained by multiplying the preset coefficient (α) with said ratio of the power setting value (Ws) relative to the maximum power value (Wmax), wherein the power adjustment value (Vfb) corresponds to a difference between the power setting value (Ws) and the current detection value and wherein the value of the coefficient (α) is larger than the power adjustment value (Vfb). a power conversion part including a switching element and receiving DC power as an input in order to adjust power supplied to a light source load by an operation to turn on/off the switching element; a control part (6, 7) receiving a power setting value (Ws) adapted to determine size of power supplied to the light source load and to control the power conversion part; a current detection part adapted to detect a current flowing in the switching element and to obtain a corresponding current detection value; a power estimation part adapted to estimate the input power (Win) of the lighting device; a presentation part adapted to present the estimated input power (Win) of the lighting device to a user or to notify the estimated input power (Win) of the lighting device to an external device, the power estimation part estimates the input power (Win) by using the power setting value (Ws) and the current detection value, thereby providing correction of the input power (Win) estimation for fluctuations of the current detection value caused by a change in the ambient temperature of the light source load by means of the following calculation: - calculating a ratio by dividing the power setting value (Ws) by a stored maximum power value (Wmax), which corresponds to the power setting value obtained in response to maximum power supplied to the light source load, and multiplying said ratio with a preset coefficient (α) to obtain a frist value, - subtracting a power adjustment value (Vfb) from said first value obtained by multiplying the preset coefficient (α) with said ratio of the power setting value (Ws) relative to the maximum power value (Wmax), wherein the power adjustment value (Vfb) corresponds to a difference between the power setting value (Ws) and the current detection value and wherein the value of the coefficient (α) is larger than the power adjustment value (Vfb). - calculating a ratio by dividing the power setting value (Ws) by a stored maximum power value (Wmax), which corresponds to the power setting value obtained in response to maximum power supplied to the light source load, and multiplying said ratio with a preset coefficient (α) to obtain a frist value, - subtracting a power adjustment value (Vfb) from said first value obtained by multiplying the preset coefficient (α) with said ratio of the power setting value (Ws) relative to the maximum power value (Wmax), wherein the power adjustment value (Vfb) corresponds to a difference between the power setting value (Ws) and the current detection value and wherein the value of the coefficient (α) is larger than the power adjustment value (Vfb).