A fishing reel, comprising: a reel unit; a handle shaft being rotatably supported by the reel unit, the handle shaft including an anti-loosening engaging portion and a male threaded portion on a tip portion thereof; a handle arm extending from a first end portion thereof to a second end portion thereof in a longitudinal direction intersecting with the handle shaft, the handle arm including an elongated hole in the first end portion thereof, the elongated hole extending in the longitudinal direction, the handle shaft being inserted in the elongated hole to be non-rotatably engaged with the handle arm, a position of the handle shaft in the elongated hole being adjustable; a handle knob being rotatably attached to the second end portion of the handle arm; a nut member (12, 42) including a body part in which a female threaded portion is formed, the female thread portion being screwed onto the male threaded portion of the handle shaft; and an anti-loosening member (24, 38, 47) being configured on the nut member (12, 42), the anti-loosening member being selectively set in a first position and a second position, the anti-loosening member (24, 38, 47) being engaged with the anti-loosening engaging portion in the first position to prevent the nut member (12, 42) from loosening, the anti-loosening member (24, 38, 47) being disengaged from the anti-loosening engaging portion in the second position to allow the nut member (12, 42) to rotate in the loosening direction, characterised in that: the nut member includes a lever part being attached to the body part and being movable away from the body part, the anti-loosening member is configured to the lever part and includes a pawl, in the first position the pawl is configured to be engaged with the anti-loosening engaging portion and the lever part is closed to the body part, in the second position the pawl is configured to be disengaged from the anti-loosening engaging portion and the lever part is opened from the body part. a reel unit; a handle shaft being rotatably supported by the reel unit, the handle shaft including an anti-loosening engaging portion and a male threaded portion on a tip portion thereof; a handle arm extending from a first end portion thereof to a second end portion thereof in a longitudinal direction intersecting with the handle shaft, the handle arm including an elongated hole in the first end portion thereof, the elongated hole extending in the longitudinal direction, the handle shaft being inserted in the elongated hole to be non-rotatably engaged with the handle arm, a position of the handle shaft in the elongated hole being adjustable; a handle knob being rotatably attached to the second end portion of the handle arm; a nut member (12, 42) including a body part in which a female threaded portion is formed, the female thread portion being screwed onto the male threaded portion of the handle shaft; and an anti-loosening member (24, 38, 47) being configured on the nut member (12, 42), the anti-loosening member being selectively set in a first position and a second position, the anti-loosening member (24, 38, 47) being engaged with the anti-loosening engaging portion in the first position to prevent the nut member (12, 42) from loosening, the anti-loosening member (24, 38, 47) being disengaged from the anti-loosening engaging portion in the second position to allow the nut member (12, 42) to rotate in the loosening direction, the nut member includes a lever part being attached to the body part and being movable away from the body part, the anti-loosening member is configured to the lever part and includes a pawl, in the first position the pawl is configured to be engaged with the anti-loosening engaging portion and the lever part is closed to the body part, in the second position the pawl is configured to be disengaged from the anti-loosening engaging portion and the lever part is opened from the body part.