A transmission processing apparatus includes a generation unit configured to generate data to be transmitted, based on an image captured by an imaging apparatus, a transmission and reception processing unit configured to receive data transmitted from a second transmission processing apparatus which is in cascade connection to the transmission processing apparatus and to transmit the received data, and a determination unit configured to determine, depending on a type of the data transmitted from the second transmission processing apparatus, whether to transmit the data generated by the generation unit in an order corresponding to the cascade connection or transmit the data generated by the generation unit in parallel with the data transmitted from the second transmission processing apparatus.