Carrier-injection and the succeeding pre-channel-formation dynamics in organic thin-film transistor was observed using time-domain reflectometry. Having previously analyzed the depth-wise variation in the initial carrier-injection from the contact electrode to the channel region, we focus here on the succeeding pre-channel-formation dynamics. We demonstrate that a hole concentration in the semiconductor/gate insulator interface increases until its electrical capacitance is filled through contact and access resistances. Thereafter, the injected-hole distribution gradually spreads. A reduction in both contact and access resistances is crucial not only for the static characteristics of the field effect transistor but also the dynamical response.