To provide an enlarging and contracting unit for simultaneously and simply using two transparent plastic underlays formed with squares of a check pattern from 0.5 cm to 3.0 cm at the time of entirely or partly enlarging or contracting a picture (original image).

When a picture is enlarged, an underlay 1 of 1.0 times is placed on an original picture 5, the underlay 1 of desired to be enlarged (or contracted) is laid on a translucent sheet (tracing paper) 6, and the picture is enlarged or contracted by drawing it on the translucent sheet by matching squares of a check pattern while observing a view under the pattern of the original picture.