Direct connection between corticospinal neurons and spinal motor neurons (MNs) plays a central role in fine motor control in primates but in rodents, presence of the direct corticomotoneuronal connection is questioned at least in adults. We previously showed that MNs innervating forelimb muscles received direct cortical inputs in infant rat by optogenetic and electrophysiological methods. However, it is not known which areas of the cortex made direct connection with MNs. Here we show the distribution of corticomotoneuronal (CM) cells in the infant mouse cortex by a retrograde monosynaptic tracing with a glycoprotein-deleted rabies virus (RV-ΔG). Intramuscular injection of RV-ΔG together with adenoassociated virus (AAV) encoding rabies glycoprotein (RG) into forelimb muscles at postnatal day 6-8 (P6-8) allowed them to co-infect MNs from terminals. RV-ΔG can spread from MNs to their presynaptic neurons by complementation of RG from AAV. The RV-ΔG is unable to spread further because RG is not expressed in the presynaptic neurons, resulting in specific infection to MNs and premotor neurons. Approximately 100 MNs were co-infected by RV-ΔG and AAV in the lower cervical cord (C5 to T1) of P14 mice. Premotor neurons were found in the spinal cord, brain stem and cerebral cortex. The CM cells were widely distributed in approximately rostral two thirds of the contralateral cortex, although the majority of them resided in contralateral motor cortex. Surprisingly, the CM cells were also found in the contralateral primary and secondary somatosensory cortex as well as in the ipsilateral caudal motor and/or primary somatosensory cortex. These results confirm our previous results and indicate that the distribution of the CM cells extended far beyond the conventional forelimb area in the motor cortex at an early postnatal period.