Comparative toxicity of different groups of pesticides on Apis mellifera L. were tested in the laboratory. Commercial formulations dissolved in water from the highest dose level marked on the label were serially diluted to 10^(-6) times to carry out oral trials on each pesticide. Fungicide (Metconazole), herbicide (Glyphosate), acaricide (Amitraz) and 3 insecticides (organophosphate Fenitrothion, neonicotinoids of Thiacloprid and Thiamethoxam) were compared. Thiamethoxam and fenitrothion caused higher mortality, and amitraz showed intermediate level of mortality while herbicide and fungicide showed minimal impacts. Among neonicotinoids, Thiamethoxam was highly toxic but thiacloprid showed mortality less than 25% even at the highest concentration. LC50 values were estimated as Amitraz 197.70, Fenitrothion 2.20, and Thiamethoxam 0.188 ppm at 24 h after treatment. Fungicide, herbicide and a neonicotinoid thiacloprid were all showed low oral toxicity. This study confirmed that the old pesticide, organophosphate was highly toxic and two different toxic path way exist for neonicotinoid pesticides.