The invention provides a base station that does not cause the number of blind decodings to be increased and further can prevent the flexibility of resource allocation from degrading. A search space setting unit sets search spaces each of which is constituted by one or more control channel elements (CCEs) and each of which is to be decoded in the terminals and each of which is defined by a plurality of to-be-decoded candidates. An allocating unit places, in one of the plurality of to-be-decoded candidates included in the search space, a control channel. The number of connections of CCEs constituting the to-be-decoded candidate is associated with the number of to-be-decoded candidates. The search space setting unit causes, in accordance with the control channel to be transmitted, the association of the number of connections of CCEs constituting the to-be-decoded candidate with the number of to-be-decoded candidates to differ.