This research examines middle school mathematics teachers' views regarding implementation of mathematical tasks and their enactments. We compare their views on tasks and their implementation, and determine the causes of difference between the two using qualitative research methods. We interview sixteen middle school mathematics teachers based on their professional experience and willingness, and observe task implementations of four. According to the data, we found that the teachers with the most professional experience have difficulty to implement the tasks, they have teacher-centred mentality and they make use of their own experiences as students than of the task itself.