A range finding device comprising: a stereo camera unit comprising a stereo image processing unit; and a laser radar ranging unit comprising alight signal detection device comprising: a light receiving optical system configured to receive a reflection signal reflected from an object when irradiation light emitted from an irradiation unit hits the object and reflects from the object; a first binarization unit (44c1) configured to binarize the reflection signal received by the light receiving optical system using a first threshold value, based on a determination of whether the reflection signal intensity is equal to or greater than the first threshold value; a second binarization unit (44c2) configured to binarize the reflection signal received by the light receiving optical system using a second threshold value set with a given value similar to a noise signal intensity value, based on a determination of whether the reflection signal is equal to or greater than the second threshold value; and a time measurement unit configured to (i) measure a time difference between a time of emitting the irradiation light from the irradiation unit and a time of receiving a reflection signal intensity equal to or greater than the first threshold value or the second threshold value, and (ii) convert the time difference into distance information between the light receiving optical system and the object; wherein the stereo image processing unit is configured to calculate disparity values between pixel blocks of stereo image pairs captured by the stereo camera unit by performing block matching; and wherein, in performing said block matching, the stereo image processing unit is configured calculate a first cost C(p,d) from said stereo image pairs and a second cost C l ( p,d l) from said distance information, and to perform a weighted addition of said first cost and second cost to calculate a final cost used to calculate said disparity values. a stereo camera unit comprising a stereo image processing unit; and a laser radar ranging unit comprising alight signal detection device comprising: a light receiving optical system configured to receive a reflection signal reflected from an object when irradiation light emitted from an irradiation unit hits the object and reflects from the object; a first binarization unit (44c1) configured to binarize the reflection signal received by the light receiving optical system using a first threshold value, based on a determination of whether the reflection signal intensity is equal to or greater than the first threshold value; a second binarization unit (44c2) configured to binarize the reflection signal received by the light receiving optical system using a second threshold value set with a given value similar to a noise signal intensity value, based on a determination of whether the reflection signal is equal to or greater than the second threshold value; and a time measurement unit configured to (i) measure a time difference between a time of emitting the irradiation light from the irradiation unit and a time of receiving a reflection signal intensity equal to or greater than the first threshold value or the second threshold value, and (ii) convert the time difference into distance information between the light receiving optical system and the object; wherein the stereo image processing unit is configured to calculate disparity values between pixel blocks of stereo image pairs captured by the stereo camera unit by performing block matching; and wherein, in performing said block matching, the stereo image processing unit is configured calculate a first cost C(p,d) from said stereo image pairs and a second cost C l ( p,d l) from said distance information, and to perform a weighted addition of said first cost and second cost to calculate a final cost used to calculate said disparity values. a light receiving optical system configured to receive a reflection signal reflected from an object when irradiation light emitted from an irradiation unit hits the object and reflects from the object; a first binarization unit (44c1) configured to binarize the reflection signal received by the light receiving optical system using a first threshold value, based on a determination of whether the reflection signal intensity is equal to or greater than the first threshold value; a second binarization unit (44c2) configured to binarize the reflection signal received by the light receiving optical system using a second threshold value set with a given value similar to a noise signal intensity value, based on a determination of whether the reflection signal is equal to or greater than the second threshold value; and a time measurement unit configured to (i) measure a time difference between a time of emitting the irradiation light from the irradiation unit and a time of receiving a reflection signal intensity equal to or greater than the first threshold value or the second threshold value, and (ii) convert the time difference into distance information between the light receiving optical system and the object; wherein the stereo image processing unit is configured to calculate disparity values between pixel blocks of stereo image pairs captured by the stereo camera unit by performing block matching; and wherein, in performing said block matching, the stereo image processing unit is configured calculate a first cost C(p,d) from said stereo image pairs and a second cost C l ( p,d l) from said distance information, and to perform a weighted addition of said first cost and second cost to calculate a final cost used to calculate said disparity values.