Provided are a MIMO transmission device and a MIMO transmission method which can improve reception quality of a response signal. A terminal (100) as the MIMO transmission device maps a first and a second element of the ACK/NACK signal vector formed from ACK/NACK signals onto a first and a second stream, respectively, and transmits the elements contained in a 2SC-FDMA symbol in a single slot. In the terminal (100), a response signal vector formation unit (140) forms [a·Sack, 0] as the ACK/NACK signal vector in a first SC-FDMA symbol and [0, a·Sack] as an ACK/NACK signal vector in a second SC-FDMA symbol. A precoding unit (165) uses a unitary matrix to precode the ACK/NACK signal vector formed in the response signal vector formation unit (140).