A disposable blood test kit inserted into an instrument for measuring the blood cell deformability is provided to avoid a washing process during a blood test. The instrument comprises a disposable blood test kit (20) for directly containing the blood sample, a light emitting unit (10) disposed above the disposable blood test kit (20), and a measurement unit (30) for measuring the blood cell deformability. The disposable blood test kit (20) comprises a blood sample pot (21) for containing the blood sample, a slit channel (22) made of a transparent material, and a tiny waste blood pot (23) for collecting the tested blood sample. A differential pressure is applied to the disposable blood test kit (20) to make the stagnant blood sample flow through the slit channel (22) and to collect the tested blood sample at the tiny waste blood pot (23).