An arithmetic decoding device that decodes coded data for a transform block of a target image, comprising: a context index deriving unit configured to derive a context index for a significant coefficient flag indicating whether a transform coefficient is 0; a syntax decoding unit configured to perform arithmetical decoding of the significant coefficient flag based on a probability state designated by the context index; and a sub-block coefficient presence/absence flag decoder configured to decode a sub-block coefficient presence/absence flag indicating whether at least one transform coefficient of a sub-block position (xCG, yCG) within the transform block is a non-zero transform coefficient, in a case that the transform block is divided into sub-blocks wherein the context index deriving unit is configured to perform following functions: i) set a first common value to the context index for the significant coefficient flag that belongs to a DC component for luminance of at least two transform blocks having different sizes among the transform blocks, ii) set a second common value to the context index for the significant coefficient flag that belongs to a DC component for chrominance of at least two transform blocks having different sizes among the transform blocks, and iii) derive the context index for a significant coefficient flag included in a sub-block with the sub-block position (xCG, yCG) different from a sub-block with the DC component using a value of the sub-block coefficient presence/absence flag assigned to a first adjacent sub-block position (xCG+1, yCG) and a value of the sub-block coefficient present/absence flag assigned to a second adjacent sub-block position (xCG,yCG+1). a context index deriving unit configured to derive a context index for a significant coefficient flag indicating whether a transform coefficient is 0; a syntax decoding unit configured to perform arithmetical decoding of the significant coefficient flag based on a probability state designated by the context index; and a sub-block coefficient presence/absence flag decoder configured to decode a sub-block coefficient presence/absence flag indicating whether at least one transform coefficient of a sub-block position (xCG, yCG) within the transform block is a non-zero transform coefficient, in a case that the transform block is divided into sub-blocks wherein the context index deriving unit is configured to perform following functions: i) set a first common value to the context index for the significant coefficient flag that belongs to a DC component for luminance of at least two transform blocks having different sizes among the transform blocks, ii) set a second common value to the context index for the significant coefficient flag that belongs to a DC component for chrominance of at least two transform blocks having different sizes among the transform blocks, and iii) derive the context index for a significant coefficient flag included in a sub-block with the sub-block position (xCG, yCG) different from a sub-block with the DC component using a value of the sub-block coefficient presence/absence flag assigned to a first adjacent sub-block position (xCG+1, yCG) and a value of the sub-block coefficient present/absence flag assigned to a second adjacent sub-block position (xCG,yCG+1). i) set a first common value to the context index for the significant coefficient flag that belongs to a DC component for luminance of at least two transform blocks having different sizes among the transform blocks, ii) set a second common value to the context index for the significant coefficient flag that belongs to a DC component for chrominance of at least two transform blocks having different sizes among the transform blocks, and iii) derive the context index for a significant coefficient flag included in a sub-block with the sub-block position (xCG, yCG) different from a sub-block with the DC component using a value of the sub-block coefficient presence/absence flag assigned to a first adjacent sub-block position (xCG+1, yCG) and a value of the sub-block coefficient present/absence flag assigned to a second adjacent sub-block position (xCG,yCG+1).