ROTSE-IIId observations of the Be/X-ray transient system KS 1947+300 obtained between September 2004 and December 2005 make it possible to study the correlation between optical and X-ray activity. The optical outburst of 0.1 mag was accompanied by an increase of the X-ray flux in the 2004 observations. A strong correlation between the optical and X-ray light curves suggests that the neutron star directly accretes from the outflowing material of the Be star. The nearly zero time lag between X-ray and optical light curves suggests a heating of the disk of Be star by X-rays. No optical brightening and X-ray enhancement was seen in the 2005 observations. There is no indication of an orbital modulation in the optical light curve. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGA. Weinheim.