An optical distance measuring apparatus for irradiating ranging light on a measuring object and receiving light reflected from the measuring object to measure a distance up to the measuring object, comprising: a light source configured to emit ranging light; a variable reflection angle mirror configured to scan the ranging light on the measuring object; an avalanche photo diode configured to receive light reflected from the measuring object of the ranging light and to output a light receiving signal according to an intensity of the reflected light; a detected signal amplifying unit configured to amplify the light receiving signal output from the avalanche photo diode;a pulse generation unit configured to generate a pulse signal based on a comparison between the amplified light receiving signal output from the detected signal amplifying unit and a reference voltage; an amplification factor control unit; a distance calculation unit configured to detect a flight time of the ranging light based on the pulse signal output from the pulse generation unit and to calculate a distance up to the measuring object, characterised in that: the light receiving signal output from the avalanche photo diode is input to the amplification factor control unit, and the amplification factor control unit is configured to generate a target bias voltage to control the light sensitivity of the avalanche photo diode based on the light receiving signal output from the avalanche photo diode; and wherein, when in use: in a first scan period, the amplification factor control unit is configured to generate the target bias voltage based on the light receiving signal output from the avalanche photo diode; in a second scan period, the amplification factor control unit is configured to control the light sensitivity of the avalanche photo diode by the target bias voltage generated in the first scan period and the distance calculation unit is configured to calculate a distance up to the measuring object. a light source configured to emit ranging light; a variable reflection angle mirror configured to scan the ranging light on the measuring object; an avalanche photo diode configured to receive light reflected from the measuring object of the ranging light and to output a light receiving signal according to an intensity of the reflected light; a detected signal amplifying unit configured to amplify the light receiving signal output from the avalanche photo diode;a pulse generation unit configured to generate a pulse signal based on a comparison between the amplified light receiving signal output from the detected signal amplifying unit and a reference voltage; an amplification factor control unit; a distance calculation unit configured to detect a flight time of the ranging light based on the pulse signal output from the pulse generation unit and to calculate a distance up to the measuring object, characterised in that: the light receiving signal output from the avalanche photo diode is input to the amplification factor control unit, and the amplification factor control unit is configured to generate a target bias voltage to control the light sensitivity of the avalanche photo diode based on the light receiving signal output from the avalanche photo diode; and wherein, when in use: in a first scan period, the amplification factor control unit is configured to generate the target bias voltage based on the light receiving signal output from the avalanche photo diode; in a second scan period, the amplification factor control unit is configured to control the light sensitivity of the avalanche photo diode by the target bias voltage generated in the first scan period and the distance calculation unit is configured to calculate a distance up to the measuring object. in a first scan period, the amplification factor control unit is configured to generate the target bias voltage based on the light receiving signal output from the avalanche photo diode; in a second scan period, the amplification factor control unit is configured to control the light sensitivity of the avalanche photo diode by the target bias voltage generated in the first scan period and the distance calculation unit is configured to calculate a distance up to the measuring object.