In an ultrahigh sensitive NMR apparatus, a stability of a temperature of a very low temperature probe coil is improved. A low temperature probe of the high sensitive NMR apparatus is structured at a very low temperature by a cooling apparatus. A cooling medium at a room temperature (300 K) discharged from a compressor is cooled down to 70K by a countercurrent heat exchanger, and is next cooled down to 4K or less by a series of second stages. Further, the cooling medium enters into a low temperature probe via a transfer tube, cools a probe coil to 5 to 10K by a heat exchanging portion, further cools a radiation shield to 40 to 60K, and makes a circuit via the countercurrent heat exchanger. A high temperature stability can be applied to a receiving probe coil in the low temperature probe by a cooling apparatus having a high temperature stability.