A computer-implemented method for determining a rectangular moving image region displayed in part of a display region, the display region having pixels arranged in row (α) and column (β) directions therein, the method comprising: a moving unit block judgment step of dividing the display region into unit blocks (110, 111,112) each including a predetermined number of pixels and judging whether each unit block (110, 111,112) is a moving unit block having a motion; characterized by a moving column block determination step of defining, as a column block, a set of unit blocks (110, 111,112) included in a column of the unit blocks,-and if one column block includes at least one moving unit block, determining the column block as a moving column block; a moving row block determination step of defining, as a row block, a set of unit blocks included in a row of the unit blocks, and if one row block includes at least one moving unit block, determining the row block as a moving row block; a first rectangular moving image region determination step of determining, as a rectangular moving image region, a rectangular region specified by unit blocks included in both the moving row block and the moving column block; and a second rectangular moving image region determination step of determining, as a boundary of the rectangular moving image region, a region defined by edges in peripheral unit blocks, the peripheral unit blocks forming peripheral four sides of the rectangular moving image region,on the basis of pixels in the peripheral unit blocks, of the unit blocks included in the rectangular moving image region, wherein the second rectangular moving image region determination step comprises: a) determining a row-direction boundary of the rectangular moving image region by determining the difference between the representative pixel values of two subsequent rows in the peripheral unit blocks and determining a column-direction boundary of the rectangular moving image region by determining the difference between the representative pixel values of two subsequent columns in the peripheral unit blocks; or b) determining a row-direction boundary of the rectangular moving image region based on a total number of pixels serving as row-direction edges in each row of the peripheral unit blocks, and determining a column-direction boundary of the rectangular moving image region based on a total number of pixels serving as column-direction edges in each column of the peripheral unit blocks. a moving unit block judgment step of dividing the display region into unit blocks (110, 111,112) each including a predetermined number of pixels and judging whether each unit block (110, 111,112) is a moving unit block having a motion; characterized by a moving column block determination step of defining, as a column block, a set of unit blocks (110, 111,112) included in a column of the unit blocks,-and if one column block includes at least one moving unit block, determining the column block as a moving column block; a moving row block determination step of defining, as a row block, a set of unit blocks included in a row of the unit blocks, and if one row block includes at least one moving unit block, determining the row block as a moving row block; a first rectangular moving image region determination step of determining, as a rectangular moving image region, a rectangular region specified by unit blocks included in both the moving row block and the moving column block; and a second rectangular moving image region determination step of determining, as a boundary of the rectangular moving image region, a region defined by edges in peripheral unit blocks, the peripheral unit blocks forming peripheral four sides of the rectangular moving image region,on the basis of pixels in the peripheral unit blocks, of the unit blocks included in the rectangular moving image region, wherein the second rectangular moving image region determination step comprises: a) determining a row-direction boundary of the rectangular moving image region by determining the difference between the representative pixel values of two subsequent rows in the peripheral unit blocks and determining a column-direction boundary of the rectangular moving image region by determining the difference between the representative pixel values of two subsequent columns in the peripheral unit blocks; or b) determining a row-direction boundary of the rectangular moving image region based on a total number of pixels serving as row-direction edges in each row of the peripheral unit blocks, and determining a column-direction boundary of the rectangular moving image region based on a total number of pixels serving as column-direction edges in each column of the peripheral unit blocks. a) determining a row-direction boundary of the rectangular moving image region by determining the difference between the representative pixel values of two subsequent rows in the peripheral unit blocks and determining a column-direction boundary of the rectangular moving image region by determining the difference between the representative pixel values of two subsequent columns in the peripheral unit blocks; or b) determining a row-direction boundary of the rectangular moving image region based on a total number of pixels serving as row-direction edges in each row of the peripheral unit blocks, and determining a column-direction boundary of the rectangular moving image region based on a total number of pixels serving as column-direction edges in each column of the peripheral unit blocks.