Novel therapeutic agents for myeloma are provided.A therapeutic agent for multiple myeloma containing a pyrazole compound represented by the formula (1): wherein R1 is C1-C6 alkyl, C1-C6 alkyl substituted with R17, C1-C6 haloalkyl, phenyl, phenyl substituted with a R11's or the like, R2 is a hydrogen atom, C1-C6 alkyl, phenyl or phenyl optionally substituted with e R21's or the like, R3 is a hydrogen atom or the like, X is a single bond or —(CR6, R7)n—, each of R4 and R5 is independently C1-C6 alkyl or the like, R6 and R7 are hydrogen atoms or C1-C6 alkyl, R8 is phenyl, phenyl optionally substituted with k R81's or the like, a tautomer of the compound or a pharmaceutically acceptable salt or solvate thereof, as an active ingredient.