A reference picture selection unit compares a predicted inter-coding amount indicating a predicted amount of coding required to perform inter prediction on a coding-target field and a predicted intra-coding amount indicating a predicted amount of coding required to perform intra prediction on the coding-target field. Upon determining that the predicted inter-coding amount is relatively larger than the predicted intra-coding amount, the reference picture selection unit switches the reference picture from a field having the same parity as the coding-target field to a field which is referable and temporally closest to the coding-target field.