PURPOSE: To provide an input display device having simple structure which can easily change a line width by detecting the writing pressure applied to an input pen and selecting automatically the line width in response to the writing pressure for the input and the display of the characters and patterns.

CONSTITUTION: A pen point 11 is contained in the main body of an input pen 1 at its part, and a bending plate 12 touches the pen 1 at the side opposite to the point 11. The plate 12 is set vertical to the point 11. When a user grips the pen 1 and presses the point 11 onto an input panel, etc., the point 11 moves upward and the plate 12 bends upward. Thus a piezoelectric element 13 also bends by the pressure of the plate 12. The plate 12 is made of an elastic material like brass, nickel, etc., and therefore bent by the writing pressure transmitted through the point 11. The element 13 is made of such a material which has its output voltage varying in proportion to the applied pressure and the degree of deformation of the element 13. Thus it is possible to take out the voltage applied from both electrodes of the element 13 through the output terminals 10a and 10b and then to automatically change the line width for the input display in response to the taken-out voltage.