In a coding performance evaluation assistance device (100), an extraction unit (110) extracts a plurality of motion vectors from a coded image (201). A calculation unit (120) calculates the angles of deviation and norms of the plurality of motion vectors extracted by the extraction unit (110). An accumulation unit (140) generates norm data (301) including one norm for each angle of deviation, from the results of the calculation by the calculation unit (120). The accumulation unit (140) accumulates the generated norm data (301) in a memory (105). An output unit (160) outputs information obtained from the norm data (301) accumulated by the accumulation unit (140) and indicating a search range of the motion vectors in the coded image (201).
