PURPOSE: To easily obtain a measured value of cephalo-analysis within a short time with high accuracy, by providing an indication position value take-in means for taking-in the position indicated by a position indicating means as a value of a contour line or measuring point and a computer calculating a predetermined calculation value on the basis of the value taken in the indication position value take-in means.

CONSTITUTION: An electrical waveform shaping circuit 2 divides an input signal into two signals to reverse one of them in a phase while allowing the other to generate delay and both of them are synthesized to generate density difference larger than that of the original image in a contour line part. An A/D converter 3 converts density data to 8-bit/256-gradation digital data. A computer 4 has a display 5, an operating keyboard 6, a mouth 7 and a thermal printer 8 capable of writing a curve. In order to make an unclear image easy to look, an optical sensor receives an image through an electrically controllable iris such as an LCD membrane to which control voltage is applied to more emphasize density difference or an electrical waveform shaping circuit 2 is provided behind the optical sensor to emphasize density or a contour line or the emphasis of the density or contour line is performed by the calculation due to the computer 4 or these processes are combined to form a sharp image. Further, in order to make an image easy to look and to enhance measuring accuracy if necessary, partial magnification is performed to display the image on the display.