This invention provides a medical cavity dilator made of water-absorbent resin. This cavity dilator has relatively great improvements in water absorbability and the rate of absorbing water, especially in the rate of absorbing water. It can greatly reduce patients waiting time and applicable to dilation for all cavity operations. Besides, the surface of the cavity dilator exhibits the effect of super-slipperiness after absorbing water, and thus can successfully enter a cavity without the need of applying a lubricator thereon.
