Disclosed is a method for transmitting an ACK/NACK signal for an HARQ (Hybrid Automatic Repeat reQuest) in a CA (Carrier Aggregation) system, the method including obtaining at least one transmission resource among first and second transmission resources; configuring a first table showing a relationship in which a combination of at least one of the first and second transmission resources and modulation symbols is mapped to an ACK/NACK signal, and transmitting modulation symbols corresponding to a transmission target ACK/NACK signal in the first table by using transmission resource corresponding to the transmission target ACK/NACK signal in the first table.