The purpose of this research was to measure the reasoning skills of mathematics students using a test instrument developed from mathematics routine and non-routine task. The study used research and development method. Development of the instrument and measurement of mathematical reasoning skills using procedure: items preparation (modification task), expert validation, field testing, and data analysis. The field testing involves students of senior high school (SMA Negeri 1) and students of University of Papua, Manokwari West Papua Indonesia. The data analyzed through studying the students' task solving, the transcripts of their work, interview after the test, identifying the specific task solving situations, and the arguments were supporting the strategy choice and strategy implementation. Result of research shows that student mathematical reasoning can be measured using the instrument test developed from the routine task and non-routine task. This research classifies the reasoning skills of mathematics students into two categories, imitative reasoning, and creative reasoning. Reasoning skills of mathematics students grouping results can be used by various interested institutions to evaluate the test using in mathematics instruction.