An electromagnetic relay comprising: a casing formed with an opening; a relay core member adapted for generating an electromagnetic field and inserted into said casing through said opening, said relay core member being formed with a recess having a first positioning portion and a second positioning portion which are exposed from said casing; an actuating set including an elongate magnetic component that is inserted into said first positioning portion of said recess in said relay core member and extending along a direction generally perpendicular to a direction of the electromagnetic field generated by said relay core member, and that is pivotable between a first position and a second position, and a resilient component inserted into said second positioning portion of said recess in said relay core member and pressing against said magnetic component for providing a resilient force thereto, said magnetic component being at said second position when the electromagnetic field is generated, and being biased to said first position when the electromagnetic field is not generated; a terminal set including first, second and third terminals (51, 52, 53) which are disposed on said casing, said third terminal being disposed between said first terminal and said second terminal, wherein said third terminal is biased to contact said first terminal when said magnetic component is at said first position, and said actuating set actuates said third terminal to contact said second terminal when said magnetic component is moved from said first position to said second position; and a housing accommodating said casing, said relay core member, said actuating set and said terminal set; wherein said relay core member includes a coil unit, a first mounting frame for mounting said coil unit thereon and disposed within said casing, and characterized by a second mounting frame connected fixedly to said first mounting frame for sealing said opening in said casing and formed with said recess. a casing formed with an opening; a relay core member adapted for generating an electromagnetic field and inserted into said casing through said opening, said relay core member being formed with a recess having a first positioning portion and a second positioning portion which are exposed from said casing; an actuating set including an elongate magnetic component that is inserted into said first positioning portion of said recess in said relay core member and extending along a direction generally perpendicular to a direction of the electromagnetic field generated by said relay core member, and that is pivotable between a first position and a second position, and a resilient component inserted into said second positioning portion of said recess in said relay core member and pressing against said magnetic component for providing a resilient force thereto, said magnetic component being at said second position when the electromagnetic field is generated, and being biased to said first position when the electromagnetic field is not generated; an elongate magnetic component that is inserted into said first positioning portion of said recess in said relay core member and extending along a direction generally perpendicular to a direction of the electromagnetic field generated by said relay core member, and that is pivotable between a first position and a second position, and a resilient component inserted into said second positioning portion of said recess in said relay core member and pressing against said magnetic component for providing a resilient force thereto, said magnetic component being at said second position when the electromagnetic field is generated, and being biased to said first position when the electromagnetic field is not generated; a terminal set including first, second and third terminals (51, 52, 53) which are disposed on said casing, said third terminal being disposed between said first terminal and said second terminal, wherein said third terminal is biased to contact said first terminal when said magnetic component is at said first position, and said actuating set actuates said third terminal to contact said second terminal when said magnetic component is moved from said first position to said second position; and a housing accommodating said casing, said relay core member, said actuating set and said terminal set; wherein said relay core member includes a coil unit, a first mounting frame for mounting said coil unit thereon and disposed within said casing, and characterized by a second mounting frame connected fixedly to said first mounting frame for sealing said opening in said casing and formed with said recess.