Brain waves were measured at the prefrontal(Fpl, Fp2) of learners during solving of the mathematical problems and the linguistical problems, which were categorized to left hemisphericity, and the spatial perception problems, which were categorized to right hemisphericity. Subjects were 25 boys at the second grade in middle school. The EEG(electroencephalogram) during thinking activities for problem-solving was analysed quantitatively by using FFT(fast Fourier transform). The results were as follows: 1) The θ wave among five frequency bands(θ, α , β₁, β₂, β₃) was dominant during the eyes-closed and thinking activities for problem-solving of all tasks. However, there was not much difference statistically between the left and the right EEG activity in five frequency bands. 2) By thinking activities for problem-solving, EEG activities in all frequency ranges were increased than in eyes-closed. Especially, the θ(4∼7㎐) activity showed the highest increase. 3) Spatial perception task had higher activity than mathematical task in B band at left brain(p$lt;.05) and α band at left and right brain(p$lt;.01). Also, spatial perception task had higher activity than linguistical task in B band at left and right brain(p$lt;.01). And linguistical task had higher activity than mathematical task in α band at left and right brain(p$lt;.05). 4) Brain hemisphericity was analyzed by using the activity of β₁ wave. Therefore, 12% of subjects showed left hemisphericity, 16% showed right hemisphericity, 72% showed left-right hemisphericity in eyes-closed. In spatial perception task, left hemisphericity was 36% of subjects, right was 28%, left-right was 36%. In mathematical task, left hemisphericity was 24% of subjects, right was 32%. left-right was 44%. In linguistical task, left hemisphericity was 28% of subjects, right was 40%, left-right was 32%. 5) Hemisphericities in problem-solving tasks showed meaningful positive correlations between linguistic task and spatial perception task(r=.436, p$lt;.05), and between linguistic task and mathematical task(r=.641, p$lt;.01). 6) There was a meaningful positive correlation between right hemisphericity and test scores in mathematical problem-solving task(p$lt;.05).