The effects of time pressure (TP) and attentional focus on stimulus evaluation and reaction preparation processes were investigated using P300 and the lateralized readiness potential (LRP). Event-related potentials (ERPs) were recorded from participants performing visual discrimination tasks. In this task, participants were presented a series of line pairs and required to judge whether the length of two lines were same or different. TP was manipulated by using moderate or severe response time limits. TP effects on the P300 and LRP latency were compared between two levels of discriminability, which was manipulated by stimulus intensity. The direction of two lines were fixed or randomly changed in each experimental block. In fixed-condition, participants were able to make responses with focusing attention on a specific location in stimulus display. Results indicated that P300 latency and response locked LRP latency were both affected by TP regardless of stimulus intensity. However, attentional focus did not influence TP effects on P300 latency and response locked LRP latency. These results suggest that the durations of both stimulus evaluation process and reaction preparation process were reduced by TP and that participants may use another strategy to adapt to TP other than focusing of spatial attention.