When an image is captured in a wood lumber measuring mode, a distance to wood lumber is detected. An area extracting unit 51 for a component drawing image area extracts component image areas 53A-53L of the wood lumber. A drawing generator 61 for a component drawing image selects the component image areas 53A-53L successively to generate a component drawing image 62. Among shape lines in the component drawing image 62, an eliminator 66 eliminates a paracentral shape line 71, an edge side shape line 72, a peripheral shape line 73 and determined shape lines 74. If a total pixel number of a portion where an estimated elliptical shape 76 generated by a shape estimation unit 67 is overlapped on a residual shape line 75 disposed inside a corrected drawing image 64 is more than a threshold, it is judged that the estimated elliptical shape 76 is correctly shaped. An object shape determining unit 83 extracts the estimated elliptical shape 76 as a shape of wood lumber. A size measuring unit 84 measures a size of the estimated elliptical shape. A size determining unit 85 determines an actual size of the wood lumber according to the size measured by the size measuring unit 84, the distance to the wood lumber and a focal length.