Provided is a rotary fluid machine in which the irregular contact of a crankshaft with a bearing is prevented by reducing the deflection of an intermediate shaft. A crankshaft (1) is provided with a first crankshaft section (3), a first crank pin (5), a second crankshaft section (11), a second crank pin (9), and an intermediate shaft (7). In a longitudinal cross-section including any two of the axes of the first crankshaft section (3), the first crank pin (5), and the second crank pin (9), the intermediate shaft (7) has a shape which has a first side located on the first direction (A) side, the first side (X) being provided so as to continuously connect a first side-side first connection point which is connected to the first crank pin (5) and a first side-side second connection point which is connected to the second crank pin (9), the first side-side first connection point being provided further in the first direction (A) than the first side-side second connection point.