An arithmetic decoding device for decoding coded data of a transform coefficient obtained by performing frequency transform on a target image for each unit domain, the device comprising: a sub-block coefficient presence/absence flag decoding unit configured to decode a sub-block coefficient presence/absence flag indicating whether or not one or more non-zero transform coefficient are included in each of a plurality of sub-blocks into which the unit domain is split; and a context index deriving unit configured to derive a context index from a horizontal and a vertical coordinate of a process target transform coefficient, where the context index is corresponding to a transform coefficient presence/absence flag indicating whether or not the process target transform coefficient is 0, wherein in a case where the sub-block coefficient presence/absence flag indicates not one non-zero transform coefficient in each, the right adjacent sub-block and the lower adjacent sub-block, the context index deriving unit is configured to derive: (i) a first context index in a case where a sum of a horizontal coordinate and a vertical coordinate indicating a position of the transform coefficient is equal to or smaller than a first threshold value, (ii) a second context index which is smaller than the first context index in a case where the sum is greater than the first threshold value and is equal to or smaller than a second threshold value, and (iii) a third context index which is smaller than the second context index in a case where the sum is greater than the first and the second threshold value, wherein in a case where the sub-block coefficient presence/absence flag indicates a non-zero transform coefficient in each, the right adjacent sub-block and the lower adjacent sub-block, the context index deriving unit is configured to have the first context index for all transform coefficients of the process target sub-block. a sub-block coefficient presence/absence flag decoding unit configured to decode a sub-block coefficient presence/absence flag indicating whether or not one or more non-zero transform coefficient are included in each of a plurality of sub-blocks into which the unit domain is split; and a context index deriving unit configured to derive a context index from a horizontal and a vertical coordinate of a process target transform coefficient, where the context index is corresponding to a transform coefficient presence/absence flag indicating whether or not the process target transform coefficient is 0, wherein in a case where the sub-block coefficient presence/absence flag indicates not one non-zero transform coefficient in each, the right adjacent sub-block and the lower adjacent sub-block, the context index deriving unit is configured to derive: (i) a first context index in a case where a sum of a horizontal coordinate and a vertical coordinate indicating a position of the transform coefficient is equal to or smaller than a first threshold value, (ii) a second context index which is smaller than the first context index in a case where the sum is greater than the first threshold value and is equal to or smaller than a second threshold value, and (iii) a third context index which is smaller than the second context index in a case where the sum is greater than the first and the second threshold value, (i) a first context index in a case where a sum of a horizontal coordinate and a vertical coordinate indicating a position of the transform coefficient is equal to or smaller than a first threshold value, (ii) a second context index which is smaller than the first context index in a case where the sum is greater than the first threshold value and is equal to or smaller than a second threshold value, and (iii) a third context index which is smaller than the second context index in a case where the sum is greater than the first and the second threshold value, wherein in a case where the sub-block coefficient presence/absence flag indicates a non-zero transform coefficient in each, the right adjacent sub-block and the lower adjacent sub-block, the context index deriving unit is configured to have the first context index for all transform coefficients of the process target sub-block.