A signal of the 27-day solar rotational period is often observed in cloud and lightning activities over the globe. Here we provide evidence of the 27-day periodicity of lightning activity in Japan using daily observational records of lightning for AD1989-2015. The 27-day period is detected with 4.2 standard deviations, but only in wide-area lightning activity covering more than a 10(5) km(2). The 27-day signal is more prominent around the maxima of solar decadal cycles.