Multiple choice items have been widely used. However the difficulties in understanding and solving the items have not been known well. The purpose of this study is to analyze the difficulties and errors in the process of solving multiple choice items. Twelve multiple choice items were developed based on the Unit 5 Separation of Mixtures in the 4th grade. Four items which students had hardly given the correct answer were selected and six students were chosen for interview. Interview results were analyzed with regard to the errors in the process of solving the multiple choice items. The findings of this study are as follows: I) The students who misread and misunderstand the questions choose the incorrect answers. 2) Most of the students activate daily knowledge in the process of problem solving. 3) The students who have misconception with the daily knowledge or have no experiences choose incorrect answers, while students who activate both daily knowledge and school knowledge choose correct answer. 4) The students of high level commit errors mainly in the latter part of problem solving process, but the students of low level do from early.