NOVELTY - External shape silicon block (3) is measured by making to-be-measured surface with 4 side surfaces parallel to longitudinal direction of silicon block cut out from silicon ingot, calculating coordinate of measuring points in each surface, defining 4 straight lines by calculating straight line which passes 2 points selected from measuring points for every to-be-measured surface, and calculating middle point of reference diagonal while defining diagonal of the shorter one as reference diagonal between 2 diagonals obtained by tying each of the 4 linear intersections.    USE - An external shape measuring method of silicon block e.g. (polycrystalline) silicon ingots used for solar cells.    ADVANTAGE - Appropriate product process of measuring external shape of silicon block and manufacturing method of silicon block with high dimensional accuracy are provided.    DETAILED DESCRIPTION - External shape silicon block (3) is measured by making to-be-measured surface with 4 side surfaces parallel to longitudinal direction of silicon block cut out from silicon ingot, calculating coordinate of measuring points in each surface, defining 4 straight lines by calculating straight line which passes 2 points selected from measuring points for every to-be-measured surface, calculating middle point of reference diagonal while defining diagonal of the shorter one as reference diagonal between 2 diagonals obtained by tying each of the 4 linear intersections at an angle of reference diagonal, and calculating coordinate and grinding allowance of external shape of a product block based on coordinate of middle point of reference diagonal. An INDEPENDENT CLAIM is included for manufacturing method of silicon block (3).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram for external shape measuring method of a silicon block illustrating a plot figure of the XY plane coordinates of a measuring point. (Drawing includes non-English language text).    Angles of a silicon block (AB, BC, CD, DA)