Abstract: An improved push button switching unit is proposed of which the indicia on the key top is recognizable even in a dark place. Namely, a phosphorescent layer emitting phosphorescence even in a dark place is formed on the upper surface of the key top to provide recognizability of the indicia and further the switching unit is provided with a light sensor means and a light source which is lighted when the ambient lightness is low as detected by the sensor means. When the switching unit is used continuously in a dark place, the light source repeats cycles of a lighting period, in which the phosphorescent layer accumulates the energy of light, and a dark period, in which the phosphorescent layer emits phosphorescence by means of the accumulated energy, so that the power consumption for lighting the light source can be saved.