To find the scale factor of the drawing, we need to compare the dimensions of the real-life object to the dimensions in the drawing.
In real life, the dining room is 4 meters long. We convert this measurement to millimeters for consistency, since the drawing's measurement is in millimeters.
1 meter is equal to 1000 millimeters. Therefore, 4 meters is:
\[ 4 \times 1000 = 4000 \text{ millimeters} \]
In the drawing, the dining room is represented as 1 millimeter.
Now we can find the scale factor by setting up the ratio of the real-life measurement to the drawing measurement:
\[ \text{Scale Factor} = \frac{\text{Real Life Length}}{\text{Drawing Length}} = \frac{4000 \text{ mm}}{1 \text{ mm}} = 4000 \]
To express this as a fraction:
\[ \text{Scale Factor} = \frac{4000}{1} \]
Thus, the drawing's scale factor is:
\[ \boxed{4000} \]