Following psychologist Langer's theory, this study aimed to examine the influence of conditional tasks containing inherent uncertainty on the cultivation of mindfulness. It used preceding research to develop conditional mathematics tasks corresponding to integers and rational numbers, within a 10-lesson curriculum. It divided a total of 182 middle school students in South Korea into three groups: a control group (49 participants), experimental group 1 (62 participants), and experimental group 2 (71 participants). During each of the 10 lessons, experimental group 1 was given a conditional task, while experimental group 2 received 3-4 conditional tasks. Mindfulness was measured before and after the 10 lessons, and a two-way repeated measures analysis of variance was conducted. This study's results revealed that the average scores of the subfactors of mindfulness--novelty seeking and flexibility--increased for both the experimental groups (1 and 2), but decreased for the control group. These findings empirically demonstrate the significance of conditional tasks with inherent uncertainty, in influencing students' psychological state.