An elevator group management device includes: an existing car control device controlling an existing car; a newly-installed car control device controlling a newly-installed car; an evaluation value preparing mechanism preparing evaluation values for the existing car and the newly-installed car; an assignment determining mechanism determining a car assigned to a call based on the prepared evaluation values; an existing car storage beforehand storing information concerning which of the cars is the existing car; and a weight storage beforehand storing a weighting factor for the existing car in the evaluation value. The evaluation value preparing mechanism prepares the evaluation value for the existing car by using the existing car storage information and the weighting factor. The elevator group management device can realize proper car assignment while suppressing occurrence of failure and considering operation efficiency when the existing car and newly-installed car are managed and controlled as one group.