The present invention provides a tension regulating apparatus for a chain of a leftover food treating device which comprises an agitation shaft having agitation blades and rotatably installed in an agitation tank and a rotation unit installed on one side of the agitation shaft for providing the agitation shaft with a rotational force, the tension regulating apparatus comprising: a driving sprocket engaged with a driving shaft of a driving motor provided on one side of the agitation tank; a driven sprocket connected to the driving sprocket by a connecting chain and engaged with one end of the agitation shaft; and a tension sprocket provided between the driving sprocket and the driven sprocket, for regulating the tension of the connecting chain. According to the present invention, the tension of the connecting chain connecting the driving sprocket and the driven sprocket can be regulated properly by the tension sprocket installed between the driving sprocket and the driven sprocket, in order to improve the engagement state between the connecting chain and the sprockets, thereby smoothly rotating the agitation shaft and minimizing the noise