The performance of the CDF end-plug calorimeter is described. We determined the energy resolutions to be σ/E=14.5%/ E⊕0.7% for electron and σ/E=68.0%/ E⊕4.1% for charged pion, where E is the energy measured in GeV. The response linearities satisfied our requirements. The response variations on the surface of a typical tower were measured to be 2.3% for e + and 1.6% for π +. For the photon conversion detection by the preshower detector, we obtained the detection efficiency for two minimum ionizing particles to be 90-100% for the phototube gains of (1-4)×10 5. The rate of π +'s depositing large fractions of energy in the electromagnetic section could be reduced by factors of 1.4-2.0 with keeping 95% efficiency of e +.