The present invention addresses the problem of providing phosphine for fumigation, by which clogging of a pipe of a fumigation gas feed device due to impurities is effectively suppressed and which has low spontaneous ignitability. The present invention also addresses the problem of providing a phosphine fumigation method in which clogging of a pipe of a fumigation gas feed device and a possibility of spontaneous ignition are reduced and which is safe. The phosphine for fumigation of the present invention has a P4 content of 10 mass ppm or less and a water content of 10 mass ppm or less. The fumigation method of the present invention includes fumigating a material to be fumigated, using phosphine having a P4 content of 10 mass ppm or less and having a water content of 10 mass ppm or less.