A rangefinder. A main body includes a first end and a second end opposite to the first end. The second end includes at least one guide bar. A receiving lens is connected to the first end of the main body. A first adjusting wheel and a second adjusting wheel are rotatably connected to the second end of the main body. A movable board is movably fit on the guide bar of the second end of the main body and is disposed between the first and second adjusting wheels. A receiving member is connected to the movable board, receiving light beams received by the receiving lens. The movable board is moved by rotation of the first and second adjusting wheels, driving the receiving member to move on an optical axis.