A trapdoor one-way function is an extended version of a zero-way permutation. A zero-way permutation was first introduced by Niemi-Renvall in Asiacrypt'94. In this paper we define the class of functions called no-way functions. This is an extended version of a zero-way permutation. Intuitively, a function f is no-way if, without trapdoor, both computing f and computing f-1 are hard. Li-Chida-Shizuya defined the notion of a no-way function, which is a provable-security version of a zero-way permutation. They also gave an example of a no-way function such that computing f and f-1 is proven to be as hard as breaking the Diffie-Hellman key exchange scheme. We redefine the notion of a trapdoor no-way function more preciously, classify no-way functions by the property of the trapdoor: common, separated and semi-separated trapdoor no-way, give a method for constructing trapdoor no-way functions from trapdoor one-way functions, and also give an example of trapdoor no-way functions.