A processor device for an endoscope, comprising: a distance acquisition unit that acquires a first observation distance that is a non-magnified observation distance between a distal end portion of the endoscope and an observation target and at least one specific observation distance that is a magnified observation distance; a distance ratio calculation unit that calculates a distance ratio between the first observation distance and the specific observation distance; an image signal acquisition unit that acquires an image signal by imaging the observation target with the endoscope at the first observation distance; a blood vessel index value calculation unit that calculates a first blood vessel index value of a blood vessel of the observation target by digitizing information regarding a blood vessel from the image signal acquired at the first observation distance; characterized in that: the first blood vessel index value comprises distance-invariant blood vessel index values and distance variant blood vessel index values; and that the processor device further comprises: an index value correction unit configured to calculate a second blood vessel index value at the specific observation distance; wherein the index value correction unit is configured to receive the first blood vessel index value of the non-magnified observation distance and to correct the distance variant blood vessel index values of the first blood vessel index value according to the distance ratio and not change the distance-invariant blood vessel index values of the first blood vessel index value. a distance acquisition unit that acquires a first observation distance that is a non-magnified observation distance between a distal end portion of the endoscope and an observation target and at least one specific observation distance that is a magnified observation distance; a distance ratio calculation unit that calculates a distance ratio between the first observation distance and the specific observation distance; an image signal acquisition unit that acquires an image signal by imaging the observation target with the endoscope at the first observation distance; a blood vessel index value calculation unit that calculates a first blood vessel index value of a blood vessel of the observation target by digitizing information regarding a blood vessel from the image signal acquired at the first observation distance; characterized in that: the first blood vessel index value comprises distance-invariant blood vessel index values and distance variant blood vessel index values; and that the processor device further comprises: an index value correction unit configured to calculate a second blood vessel index value at the specific observation distance; wherein the index value correction unit is configured to receive the first blood vessel index value of the non-magnified observation distance and to correct the distance variant blood vessel index values of the first blood vessel index value according to the distance ratio and not change the distance-invariant blood vessel index values of the first blood vessel index value. the first blood vessel index value comprises distance-invariant blood vessel index values and distance variant blood vessel index values; and that the processor device further comprises: an index value correction unit configured to calculate a second blood vessel index value at the specific observation distance; wherein the index value correction unit is configured to receive the first blood vessel index value of the non-magnified observation distance and to correct the distance variant blood vessel index values of the first blood vessel index value according to the distance ratio and not change the distance-invariant blood vessel index values of the first blood vessel index value. an index value correction unit configured to calculate a second blood vessel index value at the specific observation distance; wherein the index value correction unit is configured to receive the first blood vessel index value of the non-magnified observation distance and to correct the distance variant blood vessel index values of the first blood vessel index value according to the distance ratio and not change the distance-invariant blood vessel index values of the first blood vessel index value.