A displacement detector capable of making a measurement in two directions of measurement 180 degrees different from each other without the need of a switching operation has been disclosed. This displacement detector comprises a contact arm 41 supported rotatably at a fulcrum of extension and rotation 43, first and second contacts 42A, 42B provided to the contact arm, first and second arms 21A, 21B each one end of which comes into contact with the contact arm 41, a first detection element 25 of the first arm, a second detection element 26 of the second arm, a detection section that detects the positional relationship between the first and second detection elements, a first biasing means 24A of the first arm, a second biasing means 24B of the second arm, a first stopper 30A of the first arm, and a second stopper 30B of the second arm, and a reference rotation position is a state in which the first and second arms are in contact with the first and second stoppers and also in contact with the contact arm, and when the contact arm rotates from the reference rotation position in a first or second direction, the first or second arm enters a free state.