Counter flow heat exchanger for a miniature Joule-Thompson cryocooler. The heat exchanger comprises a body formed of a bottom sheet, a second sheet, a third sheet, a fourth sheet and a top sheet. All the sheets are made of low temperature cofired ceramics and stacked one above another and fused together. The second sheet comprises a low pressure flow channel along the length thereof terminating in an inflow hole at one end thereof and in an outlet hole at the other end thereof. The third sheet comprises an inflow hole at one end thereof corresponding to and matching with the inflow hole in the second sheet and an outlet hole at the other end thereof corresponding to and matching with the outlet hole in the second sheet. The fourth sheet comprises a high pressure flow channel along the length thereof, an inflow hole at one end thereof corresponding to and matching with the inflow hole in the third sheet and spaced apart from corresponding one end of the high pressure flow channel, an inlet hole terminating at the inception of the high pressure flow channel and an outlet hole corresponding to and matching with the outlet hole in the third sheet and spaced apart from the inlet hole in the fourth sheet. The top sheet comprises an inlet hole corresponding to and matching with the inlet hole in the fourth sheet and an outlet hole corresponding to and matching with the outlet hole in the fourth sheet and a narrow flow path between the fourth sheet and top sheet communicating with said one end of the high pressure flow channel and the inflow hole in the fourth sheet