The present technology relates to an encoding device and an encoding method, and a decoding device and a decoding method that are capable of reducing the calculation amount of orthogonal transform processing or inverse orthogonal transform processing. A DWT unit (91) performs a DWT of which the calculation amount is smaller than that of a KLT for residual information. KLT units (92-0 to 92-8) perform separable-type KLTs for a low-frequency component of the residual information that is acquired as a result of the DWT using bases of KLTs of the corresponding intra prediction modes. A coefficient acquired as a result of the KLT and a high-frequency component of the residual information that is acquired as a result of the DWT are losslessly encoded. The present technology can be applied to, for example, an image encoding device.