©2019 The Physical Society of Japan We report a Keldysh-like model for the electron transition rate in dielectrics under an intense circularly polarized laser. We assume a parabolic two-band system and the Houston function as the time-dependent wave function of the valence and conduction bands. Our formula reproduces the experimental result for the ratio of the rate of excitation under linear polarization to that under circular polarization for α-quartz. This formula can be easily introduced into simulations of nanofabrication using an intense circularly polarized laser.