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 context used for decoding the significant differential coefficient information of a target differential coefficient that is a decoding target based on a neighboring significant index, wherein the neighboring significant index is a sum of the significant sub block information of a right side decoded sub block of a target sub block that is a decoding target and the significant sub block information multiplied by 2 of a lower side decoded sub block of the target sub block, and position of the target differential coefficient in the target sub block, wherein the context deriver derives the context based on vertical position of the target differential coefficient in the target sub block in case that the neighboring significant index is 1 and derives the context based on horizontal position of the target differential coefficient in the target sub block in a case that the neighboring significant index is 2. 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 context used for decoding the significant differential coefficient information of a target differential coefficient that is a decoding target based on a neighboring significant index, wherein the neighboring significant index is a sum of the significant sub block information of a right side decoded sub block of a target sub block that is a decoding target and the significant sub block information multiplied by 2 of a lower side decoded sub block of the target sub block, and position of the target differential coefficient in the target sub block, wherein the context deriver derives the context based on vertical position of the target differential coefficient in the target sub block in case that the neighboring significant index is 1 and derives the context based on horizontal position of the target differential coefficient in the target sub block in a case that the neighboring significant index is 2.