Drive control is performed taking into account errors in the position of a subject vehicle obtained from a position calculating device. A drive control device is provided with: a position calculating device (220) which calculates a predicted location of the subject vehicle; a position range calculating unit (201b) which calculates a range of positions in which the conveying vehicle may be present, with a pre-determined expected probability, centered around the predicted location; a maximum divergence amount calculating unit (602) which calculates a maximum amount of divergence, comprising the maximum value from among amounts of divergence between a target route of the subject vehicle and each location contained in the position range; a target vehicle speed determining unit (603) which, if the maximum amount of divergence is relatively large, sets the target vehicle speed of the conveying vehicle to be relative low; and a target route tracking unit (201g) which performs control to drive the conveying vehicle along the target route in accordance with the target vehicle speed.