The effect of the bend of an interface to which electrons are confined is studied. It is shown that there appears an attractive potential due to the curvature in the two-dimensional effective Hamiltonian of an electron. The effect of an external magnetic field can be taken into account by simply replacing the momentum operators P triple overdot i in the effective Hamiltonian with P triple overdot i + (e/c)A triple overdot i, as far as the field is within the range of ordinary strength. Some examples of curved interfaces are studied. An interesting behaviour of electrons is found in the case of a circular cone, that is "fall" of electrons to the vertex.