The present study focused on the effects of avoidance of failure on the trend of trials of insight problem solving.First, we hypothesize that the stronger avoidance of failure becomes, the more likely participants will avoid the same or a similar trial, and the avoidance of failure induces the diversity of participants' reactions. Our second hypothesis is that if some participants' avoidance of failure is relatively strong, they will reach the goal with the lesser trials than other participants whose avoidance is not so strong. In order to examine these hypotheses, we conducted psychological experiments as follows: 28 participants were asked to solve an insightful pictorial puzzle controlled by a PC. As the experimental group, 13 participants tried to solve the puzzle with teacher signals, which indicate the trial has been already tried when the participant repeated the same one. 15 participants tried to solve the puzzle without these teacher signals as the control group. The effect of participants' avoidance of failure was examined by comparing the experiment group and the control group. The results revealed that avoidance of failure affected the diversity of trials, the number of trial and the solution time. Effect of avoidance of failure on so-called implicit learning during a trial were discussed. Our discussion proposed the expansion of the previous model (Jimura et al., 1999; Komazaki, 2001) which explained the effect of implicit learning.