A picture decoding device that is configured to decode a bitstream in which differential information between a picture that is a decoding target and a picture that is a prediction target is partitioned into a plurality of sub blocks, and the partitioned sub blocks are coded in a predetermined sequence, the picture decoding device comprising: a significant sub block information decoder that decodes significant sub block information that represents whether or not all the values of differential coefficients belonging to the sub block are zero; a significant differential coefficient information decoder that is configured to decode significant differential coefficient information that represents whether or not the value of the differential coefficient is zero; a differential coefficient value decoder that is configured to decode the value of the differential coefficient; and a context deriver that is configured to derive a neighboring significant index, wherein the neighboring significant index is a sum of the significant sub block information of a decoded sub block that is neighboring to the right side of the sub block that is a decoding target and the significant sub block information multiplied by 2 of a decoded sub block that is neighboring to the lower side of the sub block that is a decoding target, and to derive a context used for decoding the significant differential coefficient information of the differential coefficient that is a decoding target based on the neighboring significant index and the position of the differential coefficient that is the decoding target in the sub block that is the decoding target, wherein the context deriver is configured to derive the context without referring to the significant differential coefficient information that belongs to the sub block that is the decoding target. a significant sub block information decoder that decodes significant sub block information that represents whether or not all the values of differential coefficients belonging to the sub block are zero; a significant differential coefficient information decoder that is configured to decode significant differential coefficient information that represents whether or not the value of the differential coefficient is zero; a differential coefficient value decoder that is configured to decode the value of the differential coefficient; and a context deriver that is configured to derive a neighboring significant index, wherein the neighboring significant index is a sum of the significant sub block information of a decoded sub block that is neighboring to the right side of the sub block that is a decoding target and the significant sub block information multiplied by 2 of a decoded sub block that is neighboring to the lower side of the sub block that is a decoding target, and to derive a context used for decoding the significant differential coefficient information of the differential coefficient that is a decoding target based on the neighboring significant index and the position of the differential coefficient that is the decoding target in the sub block that is the decoding target, wherein the context deriver is configured to derive the context without referring to the significant differential coefficient information that belongs to the sub block that is the decoding target.