An encoder includes circuitry and memory coupled to the circuitry. The circuitry, in operation: generates (i) a first quantization matrix for transform coefficients included in a current block to be processed and (ii) a second quantization matrix for transform coefficients included in a low frequency domain among the transform coefficients included in the current block; and quantizes the transform coefficients included in the current block using at least one of the first quantization matrix or the second quantization matrix, in accordance with a size of the current block.