We report on the relationship between a pulsating aurora and a relativistic electron microburst using simultaneous observations of ground-based fast auroral imagers with the FIREBIRD-II CubeSat for the first time. We conducted a detailed analysis of an event on October 8, 2018 and found that the occurrence of the pulsating aurora with internal modulations corresponds to the flux enhancement of electrons with energy ranging from similar to 220 keV to >1 MeV detected with Flight Unit 4, one of FIREBIRD's CubeSat, with a time delay of similar to 585 ms. Combining of this time delay result and time of flight model, we suggest that the pulsating aurora and the microburst occur simultaneously due to the chorus waves at different latitudes along the same field-line as predicted by Miyoshi et al. (2020, ).