PURPOSE: To accurately and easily measure the depth of the concave face of a soft contact lens by a contact stylus while placing the concave face on the lower side of the lens under water, by keeping the top of the convex face of the lens out of the water.

CONSTITUTION: A container 1 is filled with water 2. A soft contact lens 3 is set in the center of the water 2 so that the concave face of the lens is located on its lower side and the top of the convex face of the lens remains over the water. A contact stylus 6 has a threaded part 7 and is moved up by rotating a knob 9. The moment the tip 5 of the contact stylus 6 comes into touch with the bottom 4 of the concave face the indicated value of graduations 8 is read to determine the depth d of the concave face. When the top of the convex face of the lens is in contact with the surface of the water, the lens is prevented from horizontally rocking. This results in accurately and easily measuring the depth of the concave face of the lens.