A physical unidirectional communication apparatus and method intended to utilize a structure that exploits an electrical signal by which data cannot be transmitted and to guarantee the reliability of data transmission via a transmission method that uses the structure. The physical unidirectional communication apparatus includes a unidirectional data transmission line, a data reception status transmission line, an internal network connection system unit for performing communication with an internal network transmission host and transmitting transmission data to an external network connection system unit through the unidirectional data transmission line, and the external network connection system unit for performing communication with an external network reception host, receiving the transmission data from the internal network connection system unit, generating reception status information of the transmission data, and transmitting the reception status information to the internal network connection system unit
