To provide a shaft vibration measuring device capable of easy non-contact measurement of a shaft vibration quantity of a rotary shaft body in an axis direction and a diameter direction.

The shaft vibration measuring device includes: a reflection pattern in which a light reflection part and a light non-reflection part are alternately arranged in the circumferential direction of the rotary shaft so that a line of width change parts is formed in a circular form in the direction; first and second light beams emitted to predetermined positions of the reflection pattern during rotation of the rotary shaft; and a light receiving/calculation part for determining a shaft vibration quantity component of a rotary shaft body in the axis direction based on a change in a light receiving time of the first light beam which appears in electric pulse signals generated in accordance with timings of reception and non-reception of respective reflected light beams of the light beams from the predetermined positions or the reflected light beams in an overlapping state and determining a shaft vibration quantity component of the rotary shaft body in the diameter direction based on the irradiation angle of the second light beam, a change in the light receiving time of the reflected light beam of the second light beam which appears in the electric plus signals, and the shaft vibration quantity component in the axis direction.