LIGHTING DEVICE AND LUMINAIRE

A lighting device includes: a DC/DC converter including two switching elements connected in series and a resonant circuit connected to a connection point between the two switching elements; and a control unit configured to control driving of the two switching elements. The control unit is configured to: perform intermittent driving in which a switching period and a non-switching period are alternately repeated, the switching period being a period in which the control unit switches ON and OFF the two switching elements respectively and inversely; and the non-switching period being a period in which the control unit stops switching ON and OFF the two switching elements; and provide, in an initial part of the switching period, a frequency gradual decrease period in which a driving frequency for driving the two switching elements is gradually decreased.