A small-sized and low-cost transmission apparatus and a transmission method (having a high responsivity) capable of transmitting an interrupt signal with a small number of input/output terminals (without a dedicated line for interrupt signals) are provided. A first transmission apparatus of the present invention comprises a central processing unit for carrying out an interrupt process in response to an interrupt signal; an input/output section having at least one data line for transmitting data signals between a second transmission apparatus and the first transmission apparatus and for transmitting an interrupt signal from the second transmission apparatus to the first transmission apparatus; and an interrupt signal detecting section for detecting an interrupt signal from among signals transmitted from the second transmission apparatus via the data line.